A Chicago marijuana dispensary security guard shot and killed a man who attacked him with an ax, police say.

It happened Monday morning at Zen Leaf Dispensary on the city's near west side, about an hour after the business opened for the day.  

Just after 10 a.m., a man got into an argument outside the business with a 37-year-old man working security there, police told FOX 32 Chicago. 

"I was very surprised. It’s definitely scary," Kwesi Mintah told the station. "You show your ID, walk in, walk out – usually no commotion or anything."

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Scene outside Chicago dispensary after security guard shoots man who attacked him with an ax

Chicago security guard fatally shoots man who attacked him with an ax outside pot dispensary. (FOX 32 Chicago)

Once things escalated the offender began to swing an ax at the security guard, slashing him in the leg. The two then began struggling, and the security guard fired shots at the offender.

The offender was taken to a hospital where he was pronounced dead. 

Police have not said if the offender was a dispensary customer.

The security guard was taken to a hospital with cuts to his left leg. He was last reported in good condition.

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"Just baffling, and I wouldn’t expect it to happen at this Zen Leaf," Sam Forbes told FOX 32. "The staff that work here are really nice, so it’s just unfortunate that it happened at this location and at all really."

A representative with Zen Leaf confirmed to FOX 32 over the phone that an incident took place Monday morning – and that the store was closed until further notice.

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"According to court records, the alleged attacker had a warrant out for his arrest for armed assault. He also faced criminal charges for unlawful use of a weapon, aggravated assault with a handgun, and resisting police," CWB Chicago reports.