The shooting happened just after 9 p.m. at the St. Moritz Gardens Apartments in the 14700 block of Washington Avenue.
Police say both teens found shot at the scene were taken to the hospital, where one died and the other is in stable condition.
They are working on a motive for the shooting, and are also searching for at least one suspect.
Witnesses are asked to contact the San Leandro Police Department at 510-577-2740 and select option 8.
Stay with ABC7 News for updates on this developing story.