The 15-year-old who took a class of 23 students hostage on Monday afternoon at Marinette High School in Wisconsin has died from a self-inflicted wound.

The student, who shot himself as police breached the classroom door, had been hospitalized with life-threatening injuries, following the nearly six-hour standoff. He has been identified as Samuel Hengel.

Police breeched the classroom door at 8:03 p.m., after a second round of shots were fired inside the classroom. Shots had been fired at 4 p.m. After tactical officers breached the classroom door, a Marinette PD officer jumped on the student to end the threat, Chief Jeff Skorik said in a late-Monday briefing.

Police said the hostages were freed unhurt, in part because the hostage-taker provided the teacher with unfettered access to authorities during the barricade, reports the Milwaukee Journal Sentinel.

Police say it's unclear why the student brought two handguns (a 9mm and .22) and a duffle bag of ammunition to school.

Student Zach Campbell told NBC's local affiliate TMJ4 that the subject appeared suicidal and didn't threaten the other students. Campbell and classmate Austin Biehl told that the student had not been bullied at school.

VIDEO — View Marinette Police Chief Jeff Skorik's Monday evening briefing, courtesy of the Associated Press: