Officers arrived at a chaotic scene on Sunday night and had to call for help after a hostile crowd emerged from the complex, San Bernardino police spokeswoman Sadie Albers said. She said investigators are still trying to determine how the shooting unfolded, what preceded it and whether there was an exchange of gunfire.
"Most of the witnesses are being uncooperative, so we're not really sure what happened prior to the shooting," she said. Evidence at the scene showed handguns and rifles were used, police have said.
Seven adults and a 17-year-old boy at the complex were shot. Albers said the 17-year-old and one adult were critically wounded. The six other victims had wounds that were not life-threatening and were expected to survive.
Police have said there is gang activity in the area, but it's too early in the investigation to attribute the shooting to gang rivalry.