California staggered by deadly back-to-back mass shootings

Just two days after a gunman killed 11 people at a Los Angeles-area dance studio, seven victims were shot dead in an agricultural area near San Francisco on Monday, as California suffered one of its bloodiest spates of mass gun violence in decades.

The authorities said they had not identified the motive for either of the rampages, which seemed especially baffling in part because the suspects in each were men of retirement age, much older than is typical for perpetrators of deadly mass shootings that have become numbingly routine in the United States.

California Governor Gavin Newsom was visiting wounded survivors from Saturday night's massacre in the Los Angeles suburb of Monterey Park when he was informed of Monday's killings in northern California.

"Tragedy upon tragedy," he wrote on Twitter.

Otherwise, the back-to-back shootings appeared to have little in common.

The latest spasm of gun carnage struck the coastal town of Half Moon Bay, about 48km south of San Francisco, where a gunman opened fire on farm workers at two locations about 1.6km apart, leaving a total of seven dead and one badly wounded, then fled.

The accused gunman, identified as Zhao Chunli, 67, was taken into custody a short time later, after he was found sitting in his vehicle, parked outside a sheriff's station, where the authorities said they believe he had come to turn himself in.