Determination unanimously confirmed without costs and petition dismissed. Memorandum: Petitioner, an inmate at Attica Correctional Facility, seeks to annul a determination that he possessed a weapon and assaulted another inmate in violation of inmate rules 113.10 and 100.10 ( 7 NYCRR 270.2[B][14] [i]; [1][i]). Petitioner failed to exhaust his administrative remedies with respect to his contention that he was denied adequate prehearing employee assistance by failing to raise it in his administrative appeal ( see, Matter of Rodriguez v. Coughlin, 219 A.D.2d 876; Matter of Nelson v. Coughlin, 188 A.D.2d 1071, appeal dismissed 81 N.Y.2d 834). We reject petitioner's further contention that the determination is not supported by substantial evidence. The hearing evidence establishes that, prior to the incident, all inmates in the cell area with the exception of petitioner had been locked in their cells and that petitioner was the only inmate with the mobility and opportunity to stab his fellow inmate. Although entirely circumstantial, the proof constitutes substantial evidence in support of the determination ( see, Matter of Hay v. Coombe, 229 A.D.2d 1015, lv denied 88 N.Y.2d 816; Matter of Motell v. Napolitano, 186 A.D.2d 989, 990). Petitioner's testimony that the victim was despondent and that the injury was self-inflicted presented an issue of credibility for the Hearing Officer to resolve ( see, Matter of Hay v Coombe, supra; Matter of Hawkins v. Coombe, 225 A.D.2d 1095, 1096). (CPLR art 78 Proceeding Transferred by Order of Supreme Court, Wyoming County, Dadd, J.)