• Mass killings that unfold in public places are a small fraction of all U.S. mass killings.
  • Workplace killings by employees are rare, criminologist James Alan Fox says.
  • Since 2006, about 3% of total mass killings occurred at a workplace and were perpetrated by a current or former employee.

Six people were killed and several others were injured after authorities say a store manager opened fire at a Walmart in Chesapeake, Virginia, on Tuesday night, another in a string of fatal shootings across the nation.

Officers found the shooter dead of an apparent self-inflicted gunshot wound.

The attack, which took place in the store break room, comes days after at least five people were killed and at least 17 injured at the Club Q shooting in Colorado Springs, Colorado.

So far this year, 202 people have died in 40 mass killings across the nation, according to a database of mass killings maintained through a partnership between USA TODAY, The Associated Press and Northeastern University.

Mass killings that unfold in public places are a small fraction of all U.S. mass killings. Those that occur at a workplace are an even smaller portion.

And workplace killings by employees are comparatively rare, say experts such as James Alan Fox, a criminologist and professor at Northeastern University. Here’s what to know.

THE LATEST:Walmart manager opens fire in break room, killing 6, in Chesapeake, Virginia

How often do workplace mass killings occur?

There have been 17 mass killings at a workplace by a current or former employee since 2006, resulting in 106 deaths, according to the database. That’s about 3% of total mass killing incidents since 2006.

“In terms of workplace homicides, most are actually committed not by employees,” Fox said.

When an employee commits a workplace shooting, the assailant typically has felt wronged by the company, Fox said.

“You can’t kill the company, but still can hurt the company by killing its employees,” he said. “It’s typically anger and hostility toward the job or the company.”