Authorities say the teen who held 24 hostages in a Wisconsin classroom has potentially life-threatening injuries from a self-inflicted gunshot wound.

Marinette Police Chief Jeff Skorik said early Tuesday the 15-year-old boy is hospitalized in serious condition. He does not know where the student shot himself.

Skorik says investigators still have no clear motive for the boy's actions Monday. The chief says the boy gave no reason for holding the 23 students and teacher in a classroom at Marinette High School for about five hours. None of the hostages were hurt.

Police say the boy shot himself as police burst into the classroom Monday night. Skorik says the teen had two handguns and fired several shots inside the classroom during the standoff. He says additional ammunition was found in a duffel bag at the school.