A police chief says no evidence has surfaced yet to show a 16-year-old boy charged in a stabbing rampage at a high school outside Pittsburgh was targeting any particular student.

Chief Thomas Seefeld says a motive for the attack Wednesday on other students at Franklin Regional High School in Murrysville remains unknown.

He says reconstructing what happened remains difficult because the suspect isn't talking to police at the advice of his lawyer, and many victims are still recovering.

Alex Hribal is accused of stabbing or slashing 21 students and a guard.

Eight students remain hospitalized, four in critical condition.