Unified Police said the 9th grade boy was on the pedestrian bridge with other students when he pulled out a handgun and shot himself.
The suicide happened outside Bennion Jr. High near 6200 South and 2700 West. The teen died at Intermountain Medical Center.
Dozens of teens and parents filled the bridge, crying and comforting each other near candles and flowers.
"It's just sad to see someone I grew up with feel the only way out is suicide," Cescily Madsen, a 9th grader at Bennion Middle School, said.
Students told ABC4 Reporter Cristina Rendon the boy constantly endured bullying by dozens of classmates.
"They were just mean to him for no reason," Alicia Earl, another student, said.
Granite School District Spokesman Ben Horsley said the school will investigate any cases of reported bullying. Horsley said the teen had reached out to a counselor last year for personal reasons, but did not bring up bullying.
He said grievance counselors will be at the school Friday and the following weeks to help students deal with the tragedy.
"I just want people to know that I'm going to miss him," Cassie Stetler, a friend of the boy, said. "God has another angel in Heaven."