Karaoke can be scary, but threatening? A school custodian's impromptu after-hours karaoke performance prompted a police response when a teacher thought she was being threatened over the loudspeaker.

State police say the teacher at Booth Free School barricaded herself inside a classroom Wednesday when she mistook someone singing a Guns N' Roses song over the public address system for a threat.

She was working after hours and thought no one else was in the building. Then she heard someone say over the loudspeaker that she was going to die.

Six troopers and three police dogs showed up and found three teenagers, one of them a custodian at the school, who had been playing with the public address system.

Police say one of them sang "Welcome to the Jungle" into the microphone. The song contains the lyrics "You're in the jungle baby; you're gonna die."

The teenagers were cuffed for about 15 minutes while police investigated. They didn't realize anyone else was in the school at the time. No charges will be filed, said state police Sgt. Brian Ness.