Schools were on lockdown or closed in the Silicon Valley city of Cupertino and nearby Los Gatos as SWAT teams sought Shareef Allman, 47.
Allman was at a routine safety meeting at the quarry at about 4:30 a.m. when he became disgruntled and left, Santa Clara County Sheriff's Lt. Rick Sung said. He then returned with a handgun and rifle and started shooting people, Sung said.
Sheriff Laurie Smith said two people were pronounced dead at Permanente Quarry in Cupertino, and a third person died later at the hospital.
Six others at the quarry were wounded and taken to area hospitals, Smith said. Some of them remained in critical condition, she said.
About 15 workers were evacuated and being kept at a safe location.
Authorities located Allman's vehicle and have seized four weapons believed to belong to the suspect, Smith said.
"The challenges are the big geographical area," she said. "The challenges are that he's armed."
Around 7 a.m., authorities received a 911 call that a woman was shot in an attempted carjacking near Hewlett-Packard Co.'s Cupertino campus by a man matching Allman's description. The shooter then fled on foot.
He used a weapon similar to the gun used in the quarry shooting, and authorities were including the female carjacking victim in the official count of Allman's victims, bringing the total injured to seven.
The carjacking victim was listed in fair condition at Santa Clara Valley Medical Center, according to hospital spokeswoman Joy Alexiou.