WILKES-BARRE, Pa. (AP) - An inmate on trial for charges he slashed a guard at a Pennsylvania prison cross-examined his alleged victim shortly after the trial opened Monday.

Correctional Officer Francis Petroski says 42-year-old Joel Perez sneaked up from behind him and whispered in a heavy accent before slashing him with a homemade shank in April 2014. That happened at the state prison in Dallas, Pennsylvania.But Perez, who is representing himself, asked Petroski how he can be sure who slashed him since he didn't see his attacker. Petroski says he turned around and saw Perez who was the only Hispanic inmate within 10 feet of the incident.Petroski, a 17-year veteran guard, is still receiving psychological counseling from the attack, but has returned to work.Perez is serving a life sentence for a 1995 Lancaster County murder.