A northern California teen is in a coma after he was found unconscious with head trauma on Nov. 23, 2013, in what police say may have been a parkour stunt gone wrong. (KGO/ABC News)

A high school sophomore from northern California is in a coma after he was found badly injured and unconscious outside a school, and police said today that the 15-year-old may have fallen while attempting a parkour stunt.

Parkour is a non-competitive sport where participants treat urban areas like obstacle courses and it sometimes includes jumping from rooftops.

The teen's family told police that he had done parkour several times before with his friends including on the roof of Montgomery High School in Santa Rosa where he was found Saturday afternoon.

The boy was not a student at the school, but lived nearby, authorities said. Just months before, a friend of the teen broke his leg in a failed parkour stunt while jumping from a rooftop at the school, police said.

"His injuries are consistent with a fall, but it's difficult to say for sure at this point," Santa Rosa Police Sergeant John Cregan told ABC News today. "He could have also been victim to a violent crime. At this point we just don't know for sure."

Parkour, also called free-running, originated in France and has become popular with young Americans, as it involves jumping off of ledges, railings, rooftops and moving around urban environments with various techniques. Numerous YouTube videos have been posted of both professional and amateur parkour practitioners.

"Detectives are interviewing some of the kids who have done parkour with the boy in the past, but so far it looks like they weren't there with him," Cregan said.

The teen was found lying unconscious on the pavement near the gym with a traumatic head injury and heavy bleeding as well as with cuts and bruises on his arms and hands, Cregan said.

According to police, he told his parents he was going on a walk and less than 30 minutes later a passerby came across the teenager unconscious. The young man had no identification on him but his father saw a news story about an injured juvenile hours later and called authorities.

Investigators are reviewing campus security video to determine how the teen was injured. There are video cameras around the school that police will use to try piece together what happened, Cregan said.

Both Montgomery High School and Maria Carillo High School, where the teen is enrolled, are on Thanksgiving break for the week and officials could not be reached for comment by ABC News.