Police shot dead on Thursday a man suspected of killing three people and wounding six others during a shooting spree at a Northern California cement plant and quarry, authorities said.

Three sheriff's deputies encountered the man they recognized as the suspected gunman from Wednesday's shooting crouched behind a vehicle and armed with a pistol, Santa Clara County Sheriff Laurie Smith told reporters.

They attempted to make contact, all three deputies fired, and the suspect was pronounced dead at the scene, Smith told a news conference aired on a local radio broadcast. She said police were awaiting positive identification of the man from the coroner's office.

The suspected gunman was killed early in the morning in Sunnyvale, California, in the vicinity of a daylong manhunt for the disgruntled worker sought in connection with Wednesday's shooting rampage, Smith said.

The suspect, previously identified as Shareef Allman, believed to be in his 40s, was also suspected of shooting and wounding a Hewlett Packard worker in a carjacking attempt at the HP office campus.

Police said the violence unfolded early Wednesday morning when Allman arrived at a safety meeting at the Lehigh Southwest Cement Permanente Plant in Cupertino, then opened fire on roughly 15 of his co-workers with a handgun and rifle.

The gunman, who was in his 40s, fled in a vehicle and a short time later shot the HP employee in the company's parking lot before fleeing again on foot, prompting a search by authorities through adjacent neighborhoods, police said.

Sheriff's spokesman Sergeant Jose Cardoza said on Wednesday that Allman was described by witnesses and victims as unhappy and disgruntled, though it was not clear whether he was troubled by work, family or other issues.