A northern Wisconsin high school remained closed Tuesday after a student held 22 classmates hostage at gunpoint on Monday night.
After being trapped in a Marinette High School classroom for over five hours, the hostages all escaped unharmed.
Police say the stand-off ended when they heard three shots and broke down the classroom door where the 15-year-old gunman was holding the students and teacher.
"As officers approached, he fired one shot, injured himself in a self-inflicted gunshot wound," Marinette Police Chief Jeff Skorik said. "As far as what caused this, it seems to be a mystery. We have not been able to identify anything that precipitated this incident."
Anxious parents were then quickly reunited with their children.
Student hostage Zach Campbell said the gunman seemed depressed, but he didn't think he meant his classmates any harm.
"I didn't know really what to think. I was just hoping to get out alive," Campbell said Tuesday on CBS' "Early Show." "He didn't want to shoot any of us."
Campbell told The Associated Press that six of the gunman's close friends were in that class.
Keith Schroeder, a former Marinette middle school teacher, said he had the gunman as a student and also knows the boy's teacher well. He said the teen's family is extremely involved in all their boys' lives.
"He's a fine young man, and I'm totally taken aback," Schroeder told The Associated Press. "Surprised, flabbergasted to say the least because this is a great family. It doesn't fit any of the things or the molds that you read about people. I couldn't say enough good things about the family."
Marinette, a city of about 12,000 people, lies about 50 miles north of Green Bay on the border with Michigan's Upper Peninsula. About 800 students attend the high school, according to its website.