The attorney for a 16-year-old accused of stabbing 21 other students and a security guard at their high school said Thursday he wants to have a mental health expert evaluate the boy and hopes to have the case moved to juvenile court.

For now, Alex Hribal is charged as an adult with four counts of attempted homicide, 21 counts of aggravated assault and a weapons charge, and is being held without bond in the Westmoreland County juvenile detention center.

In an interview with ABC's "Good Morning America," attorney Patrick Thomassey acknowledged that his client stabbed the victims, and said any defense he offers will likely be based on the boy's psychological state, which he hopes to have an expert evaluate soon.

"I would assume so, yes, depending on what the mental health experts tell me," Thomassey said.

He said that, under Pennsylvania law, he will have to convince a judge that Hribal can be rehabilitated in juvenile court, which would have jurisdiction over him until he's 21. If convicted as an adult, Hribal faces likely decades in prison.

The attorney told several media outlets that Hribal was remorseful, though he acknowledged his client did not appear to appreciate the gravity of his actions. Thomassey said he is still getting to know his client, saying he spoke with Hribal only for about 20 minutes before his arraignment late Wednesday.