MARTINSVILLE, IND.: A teenage boy was shot at a central Indiana middle school shortly before classes began Friday and a fellow student is in custody, state police said.

Sgt. Curt Durnil said the victim and a 15-year-old suspect are both students at Martinsville West Middle School where the shooting took place. The Skanner News Video

The victim was airlifted to the Methodist Hospital some 30 miles away in Indianapolis and is "assumed to be in serious condition," Durnil said.

It was not immediately clear what prompted the shooting just after 7 a.m., about 20 minutes before classes usually begin. The suspect had been suspended or expelled from school earlier in the week, he said.

''We have no motive at all at this point. We're talking to witnesses and schools officials to get to the bottom of it,'' he said.

Police are still searching for the weapon, Durnil said, adding that it wasn't clear how the suspect got inside the vestibule on the west side of the school where the shooting took place.

Police believe only one shooter was involved in the incident and they have him in custody, Durnil said. Nevertheless, all schools in the district remain under lockdown as a precaution. Martinsville is a small city some 30 miles southwest of Indianapolis.

''We're still looking at all angles, to be sure," he said.

WTHR-TV in Indianapolis said police believe the shooting stemmed from a dispute that started at a school dance last weekend.

Pamela Steinway, who was at her mother's house opposite the school at the time of the shooting, said she didn't see or hear anything until police officers and firefighters arrived around 7:15 a.m., swiftly followed by droves of concerned parents.

''They was parking their cars and running up to the (school) doors trying to find out what was going on,'' Steinway said.