SANTA ROSA - Santa Rosa police still don't know how a 15-year-old boy who was found at Montgomery High School Saturday afternoon suffered serious injuries.

Police Sgt. David Linscomb said the teen might have fallen of a roof at the high school at 1250 Hahman Drive, or might have hurt himself engaging in parkour, the sport of running, climbing, vaulting or swinging from man-made obstacles in parks, playgrounds and other public places.

"We also can't rule out assault," Linscomb said.

The unidentified teen was found by a passerby lying on the pavement and partially propped up against a wall on the campus around 4 p.m. Saturday.

He was bleeding profusely from a traumatic head injury and had cuts and bruises on his arms and hands, police Sgt. John Cregan said.

The teen had no identification with him, but his father said he left his residence to take a walk not long before he was found, police said.

The boy is in a medically induced coma at Children's Hospital and Research Center in Oakland.

Linscomb said the teen had been on a roof at the school and had practiced parkour before.

The teen lives near Montgomery High School in east Santa Rosa but attends Mario Carrillo High School further north.

Police are asking any witnesses to contact them at (707) 543-3590.