A man killed four people and wounded two in a string of robberies and stabbings in California's Orange County, south of Los Angeles, before he was arrested, police said Wednesday.

It comes just days after mass killings at A Walmart in Texas and a bar in Ohio.

The 33-year-old Garden Grove man was taken into custody after he came out of a 7-Eleven store and dropped a knife and a gun that he had taken from a security guard before fatally stabbing him, police said. His name wasn't immediately released.

One person was attacked so ferociously his nose was almost cut off.

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The violence appeared to be random and the only known motives appear to be "robbery, hate, homicide," Garden Grove police Lt. Carl Whitney said at a news conference.

"We know this guy was full of anger and he harmed a lot of people tonight," he said.

The attacks took place over about two hours in Garden Grove and neighbouring Santa Ana, southeast of Los Angeles.

A man killed four people and wounded two in a string of robberies and stabbings in California's Orange County before he was arrested. Photo / AP
A man killed four people and wounded two in a string of robberies and stabbings in California's Orange County before he was arrested. Photo / AP

Lt. Whitney said police first answered a burglary report at an apartment, where no one was hurt, he said.

A bakery was then robbed; as was an insurance business and a woman was stabbed several times in the back. She is expected to survive.

A caller reported watching the stabbing from closed-circuit television, Lt. Whitney said.

Police were called back to the same apartment complex, where two men had been stabbed. One died on a balcony and another died at a hospital, he said.

A cheque-cashing business also was robbed, as well as a petrol station where a man was slashed so badly that his nose was nearly severed, Whitney said.

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The suspect's silver Mercedes was tracked to the parking lot of a 7-Eleven store in Santa Ana where the security guard was disarmed and fatally stabbed, Whitney said. An employee of a nearby Subway store was also killed.

The suspect and all the victims were Hispanic, Whitney said.