PORTLAND, Ore. — Police are searching for a gunman who left three young people hospitalized in what investigators say appears to be a gang-related shooting outside an alternative high school.

Witnesses told police there may have been a dispute outside Rosemary Anderson High School on Friday, just before the shooting occurred at a street corner.

The assailant and two other people fled, and the wounded students went to the school for help, a police spokesman said. A 16-year-old girl was critically wounded while two males were hospitalized in fair condition. Another girl was grazed by a bullet.

“Based on the investigation thus far, the shooting appears to be gang-related,” Sgt. Pete Simpson said Friday night in a statement.

Police gang investigators “feel comfortable saying this is a gang-related shooting based on some of the people involved,” Simpson added in an interview. Police said they believe the shooter has gang ties. Simpson declined to say which victims might be linked to gangs.