concurring.
11 The legal norm that governs the employer's compensation liability to this claimant is stated in Terry Motor Company v. Mixon, 1961 OK 60, 361 P.2d 180, 181. The rule settled by Mizon is that an injury inflicted upon a worker engaged in the duties of employment through an assault or prank of a coemployee (or a third person) is deemed to arise out of employment unless competent evidence should disclose that the harmed worker "acted as the aggressor, initiator or voluntary participant in the frolie or combat" that occasioned the accidental harm in contest. When the Mizon rule was formulated the law then in force cast on the employer the burden to prove and to persuade the trier that claimant's injury did not arise out of employment. Since the § 27 presumption of compensability was repealed, the claimant must now bear the onus of proving and persuading the trial tribunal that his injury arose out of employment. American Management Systems v. Burns, 1995 OK 58, 903 P.2d 288, 291-292.
{2 The dispositive issue formed by the evidence presented below was whether the claimant could be considered "aggressor, initiator or voluntary participant" in horseplay. From the critical record proof before us opposite inferences may be drawm as to claimant's involvement in the happenings immediately preceding the harm-dealing event. One of these inferences points to claimant's non-participation and the other would tend to show that he had invited the coemployee's engagement in a previously established routine of mutual combat on the job. The choice to be made between these opposite inferences was for the trier of fact-the trial tribunal. Thomas v. Keith Hensel Optical Labs., 1982 OK 120, 653 P.2d 201, 202. Its resolution of this all-important nonjurisdie-tional fact in dispute is binding on this court. Parks v. Norman Mun. Hospital, 1984 OK 53, 684 P.2d 548.
T3 I henee concur in today's opinion and in the court's disposition of the claim.