A South Seattle gang member who fatally shot a teenager at Garfield High School in 2008 has been found guilty of first-degree murder.

D’Angelo Saloy killed 15-year-old Quincy Coleman, a Central District gang member, on Halloween night 2008 while Coleman was hanging out with friends behind the school.

Coleman was shot twice in the back and died at the scene, police said.

Saloy also was found guilty last week of attempted first-degree murder for wounding a second teen, Demario Clark, who survived the shooting. Both charges carried firearms enhancements that will increase Saloy’s sentencing range.

Saloy, 22, faces between 51 and about 64 years in prison when he is sentenced Sept. 10.

Saloy was arrested in September 2012 as he walked out of the Washington Corrections Center in Shelton, Mason County, where he’d served an 11-month sentence for second-degree assault on a police officer and unlawful possession of a firearm.

Coleman was one of six teenagers fatally shot in 2008 in Seattle, a casualty of the violence between Central District gangs and those in the city’s South End, Deputy King County Prosecutor Jessica Berliner said last month at the start of Saloy’s trial.

Also killed was Pierre “Pete the Sneak” LaPointe, a friend of Saloy’s — and his death pained and angered Saloy, who wrote about LaPointe in rap lyrics and social-media posts, Berliner said.

During a 2010 conversation recorded by an informant wearing a wire for police, Saloy said that he had been “very upset about the death” of 16-year-old LaPointe, police said. He said that on the night of Coleman’s death, he and some friends had “traveled north to find someone responsible for the shooting,” according to court documents.

Police said the video from the recorded conversation also shows Saloy urinating on Coleman’s memorial marker at the high school, the documents say.

Seattle police said Coleman was a member of a Central Area gang and Saloy is a member of a South Seattle gang.

Saloy is alleged to have thrown weapons into Lake Washington near Mount Baker Beach Park, where divers later recovered four weapons, court documents said. However, the firearms were so corroded that they couldn’t be test-fired and compared with .38-caliber bullets recovered from Coleman’s body.

Seattle Times staff reporter Jennifer Sullivan contributed to this story, which includes information from Times archives.