On Sunday night, a shooting at an Indianapolis-area shopping mall left at least four people dead and two injured.

The incident, which marked another mass shooting in the U.S., once again occurred in a retail setting — and that’s becoming more common amid a general uptick in mass shootings.

The number of active shooter incidents recorded in the U.S. has grown every year, the FBI found in a 2021 study. According to the Gun Violence Archive, there were 692 shootings in 2021 and have been at least 357 mass shootings this year so far.

“It is no secret that criminal activity at retailers as has jumped significantly over the last few years,” said Karl Langhorst, an adjunct professor at the University of Cincinnati’s School of Criminal Justice and an expert on retail loss prevention and corporate security. “And unfortunately, we’re seeing a trend that those incidents are becoming more and more violent.”

As the world’s largest retailer, Walmart was the top grocery location for gun violence incidents between January 1, 2020 and May 14, with 310 incidents and 89 deaths, Guns Down America found.

With over 5,000 retail locations in the U.S. stores, 90% of Americans live within 10 miles of a Walmart store, making it more accessible — and susceptible to violence — than many other chains.

“Retail, by its very nature, is open and welcoming to all parts of society and customer bases,” Langhorst said. “And as society itself seems to be undergoing, some would say, a breakdown of civility, you’re seeing these types of things turn into the violence, much more than what we used to.”

In August 2019, 23  people died after a shooting at a Walmart in El Paso, Texas. A few days prior, a disgruntled employee at a Mississippi Walmart store killed two co-workers and injured a police officer. A few months later, two men and one woman were fatally shot in a Walmart parking lot in Duncan, Okla.

Just this week, five people, including one employee, were injured after a shooting in a Washington State Walmart.

“It does feel like there’s something unique about Walmart,” said David C. Pyrooz, an associate professor of sociology at the University of Colorado and the co-author of a 2014 study that looked at the retailer’s impact on crime.

Walmart did not return FN’s request for comment.

By comparison, there are thousands of Dollar Tree and Dollar General stores across the U.S., but shootings in these low-price stores are less common. That might be because Walmart, with its vast assortment of products across every major category and large stores, functions as a convergent space for a variety of different people. This feature, Pyrooz explained, along with its ubiquity, makes it more likely to be the scene of a violent incident.

“[Walmart’s assortment] brings together a wide range of people — whether it’s small towns or big cities — that you don’t see at the dollar store,” Pyrooz said.

Given the trend, it is crucial for retailers to maintain ongoing relationships with local law enforcement to discuss safety and preventative measures to curb violence, Langhorst explained. Additionally, many retailers have rolled out active shooter training across their staff.

“They have to have continual discussion with them and talk about crime trends, Langhorst said. “It’s also about trying to train employees to recognize when there could be a potential conflict new stores.”