The shooting occurred inside a garage at a duplex in the 1100 block of North Wall Avenue shortly before 11 p.m. Friday.
Police say a gunman walked up and opened fire on the six people who were sitting inside the garage, drinking and relaxing.
Joseph Molina, 15, of Rialto was pronounced dead at the scene. Hyden Moya, 16, of Rialto was pronounced dead at a local hospital.
As for the two other victims, officials said one was treated and released from the hospital and the other was reported to be in critical condition and undergoing surgery.
Molina's friends and relatives gathered at the scene of the shooting Saturday to mourn his death.
"I'm angry. I'm sad, you know, this is my fourth cousin that got shot and passed away," said Sylvia Molina, the victim's relative. "It's just sad. It's just so sad."
Police were traveling door-to-door Saturday searching for clues and witnesses.
The motive for the shooting remains unknown. No arrests have been made.
The unknown shooter was described as an African American adult in his 20s or 30s, but police believe more than one suspect was involved in the shooting.
Anyone with information on this case was urged to contact the San Bernardino Police Department at (909) 384-5742.