The guard was shot three times late Wednesday when he tried to stop three suspects wearing bandanas and hoodies from breaking into the business in Palmdale, said Sheriff's Capt. Don Ford said. The dispensary was identified as the Green Cactus Collective.
The guard was in critical condition at a local hospital but was expected to survive, Ford said.
"The poor guy is in a hospital recovering when he should be at home with his family eating Thanksgiving dinner," he said.
The suspects fled on foot and remain at large, Ford said, and at least one was armed with a handgun.
The dispensary itself was illegal because such businesses are not permitted in unincorporated Los Angeles County, he said.
Palmdale is about 60 miles northeast of Los Angeles.
It's not the first incidence of violence at a medical marijuana dispensary or growing operation in California.
In July, two people were shot to death at a dispensary in Bakersfield, including an unarmed security guard.
In 2011, a marijuana grower was killed in a shootout in Amador County that began when five alleged gang members tried to steal some of the marijuana. Less than a month later, two brothers were shot and killed at a marijuana farm near the small farming community of Pixley, in remote Tulare County.
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