Shareef Allman, 47, was shot in the same Sunnyvale neighborhood where police searched for more than 12 hours Wednesday after the fatal shooting spree, according to KGO-TV.
Investigators said Allman opened fire at about 4:15 a.m. at a routine safety meeting at the Permanente Quarry in the Bay Area town of Cupertino, about 10 miles west of San Jose.
Allman shot nine people, officials said. Six people were wounded, two were pronounced dead at the scene and a third died at an area hospital.
He allegedly left the meeting angry, but he came back with a handgun and rifle.
Allman's vehicle and the guns were found a few miles away in Sunnyvale, near the place where a woman was shot and wounded during an attempted carjacking.
Officials did not immediately provide details on how the shooting unfolded.