MURRYSVILLE, Pa. — The picture of Alex Hribal emerging Thursday was one of a quiet, shy teen, and a good student who may have been teased at school but showed no outward signs of unhappiness or rage before the bizarre knife assault at his high school.

Hribal was charged as an adult with four counts of attempted homicide and 21 counts of aggravated assault after police say he went on a slashing and stabbing rampage Wednesday at Franklin Regional High that injured at least 20 students and a security guard.

District Attorney John Peck said during the brief hearing later that day that Alex made some statements — after school officials and police tackled, subdued and ultimately handcuffed him — indicating he wanted to die.

Alex's lawyer, Patrick Thomassey, said the 16-year-old sophomore's parents were as stunned as the rest of the community by Hribal's outburst.

"They did not foresee this coming. They expressed absolute horror," Thomassey told the Pittsburgh Post-Gazette. He said the teenager was not a loner, nor was he aware of any instances of bullying.

"He's scared," Thomassey told the paper. "He's a young kid. He's 16, looking like he's 12. This is all still new to him."

Thomassey said Alex is a B-plus student from an "Ozzie and Harriet" home.

STORY: Students recount horror of attack

Classmate Kaitlyn Pepper, 16, told USA TODAY that Alex was so small and quiet "he was like a shadow in the hallways."

Kaitlyn, like Alex a sophomore, had a class with Hribal last year. She recalled that he was small for his age — "like a little boy," she said — and that he was teased.

"I'd witnessed people say things to him," she said. "I couldn't tell you who said it. I didn't realize it was all that bad."

She didn't know what the teasing was about, but she described it as somewhat relentless.

"They just said things. They ride him and ride him, and today was the day that he snapped," she said.

Thomassey told ABC's Good Morning America on Thursday that the defense case likely will hinge on Hribal's mental health. He said he hoped to move the charges against the teen to juvenile court, where he could be rehabilitated and avoid decades in prison.

Thomassey said Hribal is remorseful but may not appreciate the gravity of his actions.

"At this point, he's confused, scared and depressed. Over the next few days we'll try to figure out what the heck happened here," Thomassey said. "I don't think he realizes how severely injured some of these people are."