TULSA, Oklahoma - Tulsa police respond to thousands of calls a year at the four Walmart Supercenters across town, tying up time and spending taxpayer dollars.

From murders to armed robberies, even meth labs, Walmarts all around Tulsa have been the scene of them all.

Tulsa Police Officer Darrell Ross has spent so much time responding to calls at the Walmart near Admiral and Memorial, his colleagues call him "Officer Walmart."

"I remember one time when all of our cars were lined up out front and we each had someone in custody," Ross said.

A recent article in Bloomberg Businessweek shed light on how crime at Walmarts across the nation are taxing police departments.

According to the article, last year TPD responded to 2,000 calls at the four Tulsa Walmart Supercenters, compared to just 300 at the four Targets.

"Target has a lot of people on the floor. There's a lot of people between the front doors and the rest of the merchandise in the store," Ross said.

He said the teams of people watching surveillance cameras are good at what they do. That leads to more people getting caught and more calls to police to arrest them, but it's not preventing crime from happening.

Walmart does hire security, but Ross says not enough.

"They could have more people there, so that's one way to help handle things, and the other is to just get rid of self-checkout," he said. "Self-check outs is where opportunity crimes happen, where normally someone wouldn't do anything bad but they say, ‘I'm not going to pay for this,’ and throw it in the bag."

Serious violent crimes are also a problem.

In 2014, one person was shot and killed and two others injured at the east Tulsa Walmart. Back in 2011, a woman was caught making meth inside the Walmart near 81st and Lewis.

Walmart says they are trying to cut back on crime by focusing on prevention.

A spokesperson said they have upgraded technology and added employees in the self-checkout area and at store exits.