KMBC.com:

Shawnee police Maj. Dan Tennis said the owner of the business, John Bieker, was shot and three of four suspects were shot. The shooting victims all had critical injuries.

Bieker, 44, later died at an area hospital, police said.

Bieker's wife Rebecca, who co-owned the business with him, suffered minor injuries to her face. Police said it appeared that she had been punched.

Two of the suspects were found at the gun shop. Two other suspects fled into a nearby neighborhood and were found on a woman's porch.

Tennis said all the robbery suspects were in custody.

Four of the patients were taken to Overland Park Regional Medical Center, the hospital said in a news release. Two of the patients were in critical condition and two of the victims were in fair condition.

There's a video on KMBC's site with more details, but this piece of the transcript was interesting:

One thing police are trying to figure out is who ended up shooting first and how it turned into such mayhem in so short a time. Four suspects came into the Pennsylvania gun shop just past 2:00. Three suspects shot in the store. Two suspects fled on foot. They were found not far away from here.

Whenever guns are part of the interaction, the entire calculus changes. More guns increases the likelihood of fast and furious mayhem. But if media would like to investigate how exactly the escalation happened, I'm certainly open to hearing their report. Perhaps if we had enough reports telling viewers exactly why it is that confrontations turn deadly in the presence of guns, there might actually be some change.