Officers received report of the shooting at about 11 a.m. in the area of 21 16th St.
The two brothers, identified by the Contra Costa coroner's office as 20-year-old Ron Boughton and 19-year-old Bryan Boughton, were moving furniture into the apartment complex when a suspect approached them, shot them both and then fled, Sgt. Roger Buhlis said.
One of the brothers died at the complex and the other died several hours later at a hospital in Walnut Creek, Deputy Robert Duvall said.
The suspect was described to be in his early 20s, reportedly wearing a dark sweatshirt and dark baseball cap.
Anyone with information about the suspect is asked to call Detective Mike Rood at (510) 620-6625.
