Three Oregon men have been arrested in a gang-related shooting outside a Portland alternative high school just over a week ago that wounded four people, authorities said Monday.

Marquel Diamond Dugas, 18, Marquise D'Angelo Murphy, 16, and his brother Lonzo Murphy, 22, all face attempted murder charges for the Dec. 12 shooting outside Rosemary Anderson High School, Reuters reported. The suspects are also charged with assault and four counts each of unlawful use of a weapon, Portland police told Reuters.

Three people, including a 16-year-old, were treated at a hospital after the noon shooting around the corner from the high school. They have since been discharged, police said. A fourth person was injured but did not require hospital treatment.

The shooting is believed to be gang-related, but police have not specified the nature of the dispute, according to Reuters. Local authorities have reportedly been dealing with a recent spike in crime in a city that has a history of gang violence.

Rosemary Anderson High School caters to at-risk youth, including those who have been expelled, dropped out or are homeless.

Dugas and the Murphy brothers are being held on probation violations and are expected to be arraigned Tuesday.