This is an attorney disciplinary case in which the Nebraska State Bar Association (NSBA), relator, seeks to discipline Brian L. Johnson, respondent.
On May 15, 1998, the Committee on Inquiry of the Third Disciplinary District filed formal charges against respondent. The committee alleged that while representing defendants in a criminal proceeding in 1997, respondent violated Canon 1, DR 1-102(A)(1) and (5), Canon 2, DR 2-110(A)(1) through (3), and Canon 6, DR 6-101(A)(3), of the Code of Professional Responsibility. Pursuant to Neb. Ct. R. of Discipline 10(F), the NSBA filed additional charges alleging that while representing Darrin Hofmann in a specific performance case in 1997, respondent violated the same provisions of the Code of Professional Responsibility as stated above. The relevant provisions of the Code of Professional Responsibility are as follows:
DR 1-102 Misconduct.
(A) A lawyer shall not:
(1)Violate a Disciplinary Rule.
(5) Engage in conduct that is prejudicial to the administration of justice. ...
DR 2-110 Withdrawal from Employment.
(A) In general.
(1) If permission for withdrawal from employment is required by the rules of a tribunal, a lawyer shall not withdraw from employment in a proceeding before that tribunal without its permission.
(2) In any event, a lawyer shall not withdraw from employment until the lawyer has taken reasonable steps to avoid foreseeable prejudice to the rights of his or her client, including giving due notice to the client, allowing time for employment of other counsel, delivering to the client all papers and property to which the client is entitled, and complying with applicable laws and rules.
(3) A lawyer who withdraws from employment shall refund promptly any part of a fee paid in advance that has not been earned.
*497DR 6-101 Failing to Act Competently.
(A) A lawyer shall not:
(3) Neglect a legal matter entrusted to him or her.
In his answer to the charges, respondent filed a counterclaim against the NSBA, seeking money damages. This court has stricken the counterclaim.
This court referred the matter to a referee, pursuant to Neb. Ct. R. of Discipline 10(J) (rev. 1996). The referee conducted a formal evidentiary hearing on August 27, 1998, which respondent did not attend. Respondent had informed the referee that he would not attend the hearing before the referee unless he was given an assurance that he would not be questioned.
The referee found that the evidence clearly and conclusively established that respondent violated his oath and violated all six disciplinary rules stated above both in his representation of the defendants in the criminal proceeding and in his representation of Hofmann. In addition to these determinations, the referee noted a concern with respondent’s attitude throughout the disciplinary proceeding, finding that he “remains generally unrepentant and . . . tends to point the blame at everyone but himself, and his general decorum and responsiveness to the entire situation reflects poorly on his past and future ability to practice law.” The referee recommended that respondent be suspended from the practice of law for 2 years and that he should not be readmitted without completing a course on ethics.
In his response to the referee’s report, respondent took no exception to the referee’s factual findings or the referee’s determinations that respondent violated certain disciplinary rules. Regarding the recommended suspension, respondent agreed that he should be suspended and added that he should also be publicly censured, but asserted that the suspension should be variable and should end upon his completion of a 100-page dissertation regarding ethics, with the specific subject to be determined by this court. However, in his brief to this court, respondent (1) asserts that the referee did not consider certain mitigating evidence; (2) provides justifications for his actions; and (3) argues that in his representation of Hofmann, respon*498dent did not violate any disciplinary rule. The NSBA took no exception to the referee’s report.
STANDARD OF REVIEW
A proceeding to discipline an attorney is a trial de novo on the record, in which the Nebraska Supreme Court reaches a conclusion independent of the findings of the referee; provided, however, that where the credible evidence is in conflict on a material issue of fact, the court considers and may give weight to the fact that the referee heard and observed the witnesses and accepted one version of the facts rather than another. State ex rel. NSBA v. Malcom, 252 Neb. 263, 561 N.W.2d 237 (1997); State ex rel. NSBA v. Johnston, 251 Neb. 468, 558 N.W.2d 53 (1997). The charges against an attorney must be established by clear and convincing evidence. See State ex rel. NSBA v. Johnston, supra.
FACTS
Because respondent did not attend the hearing before the referee and did not take exception to the referee’s determinations other than the recommended discipline, we do not address his arguments in his brief that contest the referee’s findings. See State ex rel. NSBA v. Schmeling, 247 Neb. 735, 529 N.W.2d 799 (1995). We nonetheless conduct a de novo review of the record, and upon our review, we find the following facts:
Respondent was admitted to the practice of law in the State of Nebraska on September 28,1995. At all times relevant to this matter, respondent was engaged in the private practice of law in Madison County, Nebraska.
Respondent was retained by five individuals to represent them on minor in possession charges. They each paid him a fee in advance. Respondent appeared with his clients at their arraignments. He filed a motion to suppress evidence on behalf of each client. The hearing on the motion to suppress was scheduled for June 30, 1997. The clients appeared, but respondent did not. The clients waited at the courthouse and repeatedly tried to contact him. Eric Ford, one of the clients, testified that they reached respondent’s secretary but that the secretary did not know where respondent was. Respondent did not con*499tact the court or any of his clients to explain his absence. The county court continued the hearing until July 7.
On July 3 and 7, 1997, respondent filed motions to withdraw as attorney of record for the defendants, but did not attach an affidavit stating that he informed his clients of the motions to withdraw. In fact, he did not notify any of the five clients that he was withdrawing. The motions stated that he did not attend the suppression hearing because a power failure caused his clocks to fail. Respondent explained that he could no longer represent the clients because of the sale of his office building and because of conflicts with scheduled hearings. He did not appear at the hearing on July 7, although he was still attorney of record. Some of the clients unsuccessfully asserted the motion to suppress pro se, and all of the clients eventually pled guilty. When asked by one client for his money back, respondent wrote to the client stating,
A flat fee is non-refundable.... A hearing on the suppression issue would have cost you considerably more ....
I was forced to withdraw from this case through no fault of my own. The Madison County Court Judge would not let me change my local court cases to another date, and they always conflicted with your cases in Bassett.
If you have a complaint, then direct it to this judge who usurps the power of a lawyer to even request a continuance without his prior permission. I cannot help it if there are judges that will not work with attorneys and do not give them proper respect and consideration. In my opinion, this is what caused the conflict in your cases in Bassett, Nebraska. I cannot waste my time arguing with judges over scheduling matters. I have exhausted my patience with them, and with clients like you who never think they are guilty.
Ford testified that he and the other clients understood that the fee they paid would include representation up to but not including a trial. Ford’s account of the fee arrangement was contradicted only by unsworn assertions in respondent’s answer to the charges. The referee determined that respondent returned the fees in full, but only after the Committee on Inquiry conducted its hearing.
*500In the second legal matter at issue, respondent represented Hofmann in a specific performance case against Garry Pollman, Jr., in Madison County District Court. Respondent filed a petition on behalf of Hofmann. Attorney Jan Einspahr represented Pollman and filed a counterclaim in the suit. Respondent filed an answer to the counterclaim on behalf of Hofmann on May 15, 1997. A pretrial conference was scheduled for September 29.
On June 6,1997, Einspahr sent respondent a letter indicating that their two respective clients were working out a settlement without the assistance of counsel. The letter requested respondent advise her if Hofmann had told respondent of the settlement and stated that if so, they could arrange the closing on the real estate at issue. Respondent made at least one attempt to contact Hofmann by regular mail prior to the pretrial conference date. The record indicates that Hofmann did not receive the message because he had moved out of town and did not provide respondent with a forwarding address.
In a letter dated July 25, 1997, respondent wrote Einspahr and expressly noted the scheduled pretrial conference. He stated in the letter that he had little contact with Hofmann and asked Einspahr if he needed to dismiss the case. This letter was the last communication Einspahr received from respondent prior to the pretrial conference. Einspahr testified that she called respondent daily for 2 weeks but could not reach him.
Respondent failed to appear at the pretrial conference on September 29,1997, and did not contact the court to explain his absence. The court attempted to contact respondent at the time of the pretrial conference but reached an answering machine. The court dismissed Hofmann’s petition. Respondent wrote to Hofmann in a letter dated September 30, using the last address he had for Hofmann, that the court had dismissed Hofmann’s claim and that the counterclaim still existed but that respondent had not agreed to, and would not, represent Hofmann on Pollman’s counterclaim.
Trial was held on Pollman’s counterclaim, and on December 4,1997, a judgment of $5,287.91 was entered against Hofmann. Respondent did not appear at the trial on the counterclaim and did not contact the court or Einspahr to explain his absence. At *501no time did he request the court to permit him to withdraw as Hofmann’s counsel.
Einspahr mailed the judgment against Hofmann to respondent, as attorney of record. Respondent objected, stating that he was not Hofmann’s attorney and claiming that he had made no appearance on the counterclaim. Respondent asked the district court clerk to mail the judgment documents directly to Hofmann.
Hofmann later obtained other counsel and attempted to vacate the judgment against him, but was unsuccessful.
ANALYSIS
Disciplinary Rule Violations
After reviewing the record of the proceedings de novo, we find that the evidence clearly and convincingly shows that respondent violated DR 1-102(A)(1) and (5), DR 2-110(A)(1) through (3), and DR 6-101(A)(3) in his representation of the defendants in the criminal proceeding, in that he neglected a legal matter entrusted to him, engaged in conduct that is prejudicial to the administration of justice, withdrew from representation without permission from the court and without giving notice to his clients, and refused to promptly refund unearned fees. As to respondent’s representation of Hofmann, we find the evidence clearly and convincingly shows that respondent violated DR 1-102(A)(1) and (5), DR 2-110(A)(1) and (2), and DR 6-101(A)(3), in that he neglected a legal matter entrusted to him, engaged in conduct that is prejudicial to the administration of justice, and withdrew from representation without permission from the court and without taking reasonable steps to avoid foreseeable prejudice to his client’s rights. However, we find that the evidence does not clearly and convincingly support the referee’s determination that respondent violated DR 2-110(A)(3) during his representation of Hofmann. The evidence indicates that respondent might not have received a fee from Hofmann beyond that necessary to pay costs of filing the petition. Thus, we dismiss the NSBA’s charge that respondent violated DR 2-110(A)(3) in the course of his representation of Hofmann.
*502Imposition of Penalty
We now address the appropriate disciplinary measures to be taken. To determine whether and to what extent discipline should be imposed in a lawyer discipline proceeding, this court considers the following facts: (1) the nature of the offense, (2) the need for deterring others, (3) the maintenance of the reputation of the bar as a whole, (4) the protection of the public, (5) the attitude of the offender generally, and (6) the offender’s present or future fitness to continue in the practice of law. State ex rel. NSBA v. Schleich, 254 Neb. 872, 580 N.W.2d 108 (1998); State ex rel. NSBA v. Scott, 252 Neb. 698, 564 N.W.2d 588 (1997). Each case justifying discipline of an attorney must be evaluated individually in light of the particular facts and circumstances of that case. State ex rel. NSBA v. Schleich, supra. For purposes of determining the proper discipline, we consider respondent’s acts both underlying the events of this case and throughout this proceeding. See State ex rel. NSBA v. Schmeling, 247 Neb. 735, 529 N.W.2d 799 (1995); State ex rel. NSBA v. Zakrzewski, 252 Neb. 40, 560 N.W.2d 150 (1997). Cumulative acts of attorney misconduct are distinguishable from isolated incidents of neglect and therefore justify more serious sanctions. State ex rel. NSBA v. Johnston, 251 Neb. 468, 558 N.W.2d 53 (1997); State ex rel. NSBA v. Schmeling, supra.
We note that our analysis is limited to the record of the referee’s hearing. Respondent did not attend the hearing, nor was he represented by counsel. To the extent that his brief provides explanations for his actions that are not supported within the record, those arguments will not be considered. Additionally, respondent complains in his brief that the referee did not consider a packet of documents that respondent had mailed to this court and requests us to do so. Because respondent did not offer these documents into evidence at the hearing, we, like the referee, will not consider them.
In both matters at issue, respondent neglected his duty to represent his clients by failing to make court appearances. Standing alone, these errors constituted a breach of Johnson’s professional responsibility which would warrant some degree of discipline. However, respondent’s subsequent acts and omis*503sions exacerbated his original misconduct and thus increased the seriousness of his disciplinary infraction.
As to the defendants in the criminal proceedings, respondent failed to call either the clients or the court to explain his absence and failed to notify the clients that he was withdrawing. Although the referee determined that respondent’s actions were not the causal factor in his clients’ being convicted, he nonetheless left the clients to fend for themselves at a criminal proceeding. Worse, when a client demanded a refund of the fee he paid (where the evidence clearly shows that the fee paid for at least his presence at the motion to suppress hearing), respondent not only refused to refund the fee, but proceeded to attack his client’s character and chastise a judge. Thus, he wrongly retained an unearned monetary benefit at the expense of his client. Such conduct not only needs to be deterred to protect the public but also because it negatively reflects on the reputation of the entire bar.
As to the Hofmann matter, respondent neither asked the court for permission to withdraw from the case nor contacted the court to explain his absence either at the pretrial conference or at the trial on the counterclaim. He did not inform opposing counsel of his view that he was not Hofmann’s attorney on the counterclaim. In summary, respondent unilaterally decided at some point that he would no longer represent Hofmann. The decision to withdraw as counsel was not solely within respondent’s discretion. See DR 2-110(A). Hofmann lost the opportunity to assert his claim and had a judgment rendered against him without the benefit of legal representation. As the referee determined, respondent’s conduct had a direct effect on Hofmann’s civil case. This conduct reflects negatively on the reputation of the bar and should also be deterred.
Numerous facts within the record call into question respondent’s present fitness to practice law. Respondent filed an affidavit in this proceeding (filed My 22, 1998) on which he signed as both the affiant and the notary. He asserts in this civil proceeding that he had the right to remain silent and to refuse to testify. Respondent asserts that he has no continuing responsibility to a client whom he has determined to be guilty. He *504asserts, apparently misunderstanding the authority of a court order, that he did not “feel compelled to attend [the] pretrial conference, as these are mere courtesy and not even mentioned under Nebraska law ...” He asserts in this proceeding that he had no duty to represent a client on a counterclaim when he had entered an appearance on the counterclaim.
Yet another example indicating a lack of present fitness to practice law is respondent’s objection in this proceeding to the fact that another attorney, rather than Hofmann, filed the complaint to the NSBA, asserting that it is improper for an attorney to report another attorney’s conduct. Respondent fails to understand that attorneys have a duty to report unprivileged knowledge of another attorney’s violation of the Code of Professional Responsibility — a duty that can result in disciplinary action if violated. Canon 1, DR 1-103(B), of the Code of Professional Responsibility. To conclude that respondent is simply ignorant of this rule would be lamentable enough, except that he has expressly referred to the corollary Ethical Consideration 1-4 as the “Nazi rule.”
Although an attorney has the right to defend himself or herself zealously in a disciplinary proceeding, respondent’s extremely negative attitude and inflammatory and derogatory remarks toward the NSBA and the disciplinary process also weigh in favor of a harsher punishment. Early in the investigation, he threatened the Counsel for Discipline, stating:
You may expect a federal case in this issue before the expiration of the statute of limitations. Do not think for a moment that I will confine these issues to this state as there are much broader questions here, including a pattern of harassment and discrimination by your office, and your personal deniability and unaccountability. This is a Federal issue that goes directly to my ability to earn a fair living and to be free from the abuses and interference of government and meddling organizations like the NSBA, and addresses your seeming immunity to act without regard to the consequences, reason or the truth....
My second cause of action against your office is a distinct form of invidious discrimination, and your discrimi*505natory treatment of me because of the fact that I am a descendant of the Germans from Russia, a group that is clearly a minority in this country. [Y]our pattern of personal harassment against me, cover-ups of unethical conduct by others you work with, and your flagrant abuse of authority is clear!
(Emphasis in original.) In his answers to the formal charges, respondent asserted a counterclaim against the NSBA for monetary damages and stated that the Counsel for Discipline “abused his authority in a way that smacks of fascism.” Respondent accused the judge in the Hofmann matter of malice and corruption. He asserts in his brief that Hofmann’s own negligence caused the counterclaim judgment.
We have stated, “The repeated derogatory and inflammatory statements made by respondent. . . cannot be ignored and will not be tolerated. Because such tactics reflect respondent’s overall fault-finding attitude in this matter, we take them into consideration in determining an appropriate penalty.” State ex rel. NSBA v. Zakrzewski, 252 Neb. 40, 51, 560 N.W.2d 150, 157 (1997).
The determination of an appropriate penalty to be imposed on an attorney also requires consideration of any mitigating factors. State ex rel. NSBA v. Schleich, 254 Neb. 872, 580 N.W.2d 108 (1998). In the instant case, the violations were not criminal in nature, and as to the Hofmann matter, respondent did not monetarily benefit from his wrongdoing. Respondent did have difficulty contacting Hofmann to determine whether in fact the client was settling the matter without counsel. As to the defendants in the criminal proceeding, respondent admitted in the investigation that he failed to withdraw properly and that he should have told his clients he was withdrawing. We also note that at the time these violations occurred, respondent had been in practice for approximately only 2 years.
In conclusion, respondent demonstrates a current lack of character, attitude, and knowledge of his ethical duties required to continue in the practice of law. Thus, we hereby suspend respondent from the practice of law for a period of 4 years, effective immediately. Additionally, we condition his readmission to the practice upon a showing that his acts over the course *506of the 4-year suspension demonstrated the level of character and fitness enumerated in Neb. Ct. R. for Adm. of Attys. 3(a) through (d) and (j) (rev. 1998).
Judgment of suspension.
Miller-Lerman, J., not participating.