According to police, the victims were watching a softball game about 4 p.m. Wednesday when a lone gunman came up from behind them and opened fire.
The victims were identified as 19-year-old Alan Nelson Mateo and 18-year-old Salvador Diaz. A third man was shot in the leg and was hospitalized in stable condition. His name has not been released.
Authorities said Diaz fell from the bleachers when he was shot. He was pronounced dead at the scene. Mateo collapsed on the bleachers after being shot. He was rushed to a local hospital, where he was pronounced dead.
"I saw the other guy against the first guy that was shot," said witness Steve Faulkner. "He fell on top of the bleachers, and he didn't move, so I'd assumed that he was dead before he even hit the ground."
Police say the shooting may be gang related.
According to those who knew the victims, they had no gang affiliation. Mateo was described as a class clown who was supposed to graduate from Venice High School on Thursday.
"We wish we knew why him, why would you do that to him?" Mateo's friend Ana Martinez said.
Diaz had just graduated from a vocational high school last week, friends and family said. A cousin said he had enrolled in a community college to continue his education.
Authorities said a Hispanic man in his 20s fired at the victims. There was also a second suspect driving a car in which both suspects fled the scene.
There was no description of the driver, but the vehicle was a silver or gray sedan.
Anyone with information is urged to call the Los Angeles Police Department at (877) 527-3247.
The Associated Press contributed to this report.