Mass killings database: Workplace shootings remain rare

The mass shooting at a brewery in Milwaukee, Wisconsin, was the 13th in the U.S. since 2006. Workplace mass shootings remain a rare event but there are some trends among who carries them out and why.

The Associated Press/USA TODAY/Northeastern University Mass Killings database tracks all U.S. homicides since 2006 involving four or more people killed, not including the offender, over 24 hours regardless of weapon, location, victim-offender relationship or motive.

Before Wednesday's shooting at the sprawling Molson Coors plant in Milwaukee, there had been three mass shootings in the United States in 2020 and none of those had taken place at the workplace. In 2019, there were two workplace mass shootings.

Here are some of the key findings from the AP/USA Today/Northeastern database on workplace shootings:

THE PERPETRATORS:

All but one of the shooters was a man. The lone exception was in 2006 when 44-year-old Jennifer San Marco, a former postal worker with a history of mental illness, shot and killed a neighbor before traveling to the postal facility and killing six employees. She then killed herself.

The youngest was 25 while the oldest 60. Most were in their 30s or 40s. About a third were black while the rest were white.

About half of them died by suicide.

THE WEAPONS

All of the workplace shootings were carried out using handguns. In one case, 34-year-old Aaron Alexis used both a handgun and a shotgun to kill 12 and injure eight in an office building at the Washington Navy Yard in 2013. The former Navy reservist was killed by police. Alexis worked for a base subcontractor.

THE REASONS

In about half of the cases, the perpetrator had either been fired or reprimanded. In the other cases, the apparent reasons varied, with a history of mental illness being present about a quarter of the time. In at least one case — the mass shooting at a government building in Virginia Beach, Virginia, last year — authorities remain uncertain what set off the gunman.

Workplace shootings of course predate the database.

In one of the most memorable earliest workplace shootings, a 47-year-old pressman on medical leave due to psychological issues killed eight people and injured 12 before killing himself at Standard Gravure, a printing plant in Kentucky, in 1989.

The 1990s were marked by mass shootings at Chuck E. Cheese in Aurora, Colorado, where a fired employee shot and killed four workers in 1993. Later that decade, in 1999, a fired day trader killed 12 people and injured more than 13 at his home and then at two day trading offices in Atlanta. He then killed himself.

WORKPLACE LOCATION

In about a quarter of the shootings, the workplace was a government building, while the rest were carried out at commercial businesses.