Homicide detectives were trying to determine Friday whether deadly attacks on staff at two medical marijuana dispensaries were connected.

The attacks Thursday came amid concern about the proliferation of pot clinics and new city regulations that could shutter hundreds of them.

Four robbers gunned down an employee and wounded another at about 4:15 p.m. Thursday at Higher Path Holistic Care Collective on Sunset Boulevard in the Echo Park area, said Cmdr. David Doan, chief of detectives.

Killed was Matthew Butcher, 27, of Los Angeles, a coroner's official said. The other employee, whose name was not released, was hospitalized in critical condition, police said.

Five hours after the first attack, the owner of the Hollywood Holistic dispensary found the body of an employee at the Hollywood store, Doan said.

The man was in his 30s, but his name was not released. He appeared to have been stabbed to death.

There were no immediate arrests.

Investigators do not know the motive for the second killing and were unsure whether the two attacks were linked.

No surveillance video was available from either store, and detectives think video footage from Hollywood Holistic was deliberately destroyed by an employee at another clinic in the same building, said a law enforcement official who asked not to be identified because the investigation was ongoing.

Butcher's mother, Julie Butcher, told the Los Angeles Times her son had been trying to make ends meet in a tough economy.

"He was one of the most peaceful people," she said "He would have given them anything they wanted. There's no reason for anyone to die over marijuana."

Marijuana dispensaries handle large amounts of money, which could make them targets for robbers. In October 2008, a group of men walked into La Brea Collective and fatally shot a security guard during an attempted robbery.

Crime was among the concerns that prompted the City Council to crack down on pot dispensaries, which have flourished since California voters legalized use of marijuana for medical reasons in 1996.

The medical marijuana initiative did not address actual sales of the drug, and communities up and down the state have struggled to craft laws. Some have outright banned pot clinics, which call themselves collectives and supposedly only sell to members with medical problems.

New Los Angeles city regulations that took effect earlier this month bar dispensaries from being near homes, schools, churches or parks. Some began closing, and city officials have said an estimated 400 clinics could be forced out of business.

More than 130 existing dispensaries that registered before a 2007 moratorium can stay open if they prove within six months that they meet the new guidelines.

Doan said both the clinics where the shootings occurred were licensed before the moratorium.

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Associated Press Writer Thomas Watkins contributed to this report.