Chicago police said a male suspect hit a security guard with an axe in the leg during an argument outside the Zen Leaf Dispensary in the 200-block of S. Halsted around 10:05 a.m.
A struggle then ensued and the guard fired at least four shots, witnesses said.
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The suspect was taken to Stroger Hospital in critical condition, where he died, police said. He has not yet been identified.
The security guard was taken to Northwestern Hospital in good condition with lacerations to his leg.
Investigators shut down the block for several hours as they photographed evidence, including the axe that was left lying on the sidewalk and towels used to stop the security guard's bleeding wound.
Investigators haven't said if the axe-wielding offender was a potential customer. Witnesses said he was carrying the axe in a large backpack.
"That's what people in Greektown say, that the neighborhood has changed since the dispensary opened a few years ago," said Maca Navas, who lives nearby. "There's more violence and crowds that make noise, and they are aggressive sometimes.
A spokesperson for Zen Leaf Dispensaries said in a statement: "This morning outside Zen Leaf on Halsted Street, an individual attacked a contracted third party security guard with a weapon outside the dispensary. Both individuals were taken to hospitals with serious injuries. Zen Leaf will be closed for the remainder of Monday, September 5th to allow the Chicago Police Department to conduct their investigation of this incident."
The third party security company told ABC7 the guard primarily worked at that location. He is expected to be OK.
Police are hoping to find surveillance video that may indicate a motive to the bizarre, daylight attack.