According to a database of mass killings, mass shootings at the workplace remain a rare event.

The mass shooting at a brewery in Milwaukee, Wisconsin, was only the 13th since 2006.

The gunman at the Molson Coors plant killed five employees Wednesday before killing himself.

A database of mass killings tracked in partnership by The Associated Press, USA Today and Northeastern University, shows the vast majority of mass killings are carried out by men wielding handguns; about half of the gunmen were either fired or had been reprimanded on the job.