The basic pattern found by the New Jersey DHS fusion center, and obtained by Public Intelligence (.PDF), is one of a killer who lashes out at his co-workers. Thirteen out of the 29 observed cases “occurred at the workplace and were conducted by either a former employee or relative of an employee,” the November report finds. His “weapon of choice” is a semiautomatic handgun, rather than the rifles that garnered so much attention after Newtown. The infamous Columbine school slaying of 1999 is the only case in which killers worked in teams: they’re almost always solo acts — and one-off affairs. In every single one of them, the killer was male, between the age of 17 and 49.Source here.
They also don’t have military training. Veterans are justifiably angered by the Hollywood-driven meme of the unhinged vet who takes out his battlefield stress on his fellow Americans. (Thanks, Rambo.) In only four of the 29 cases did the shooter have any affiliation with the U.S. military, either active or prior at the time of the slaying, and the fusion center doesn’t mention any wartime experience of the killers. Yet the Army still feels the need to email reporters after each shooting to explain that the killer never served.
The ramifications here are important. These shooters aren't former military. They're not specially trained. The significance is that unlike what the DHS will tell you, your best solution isn't to hide or try to stab them in the feet with scissors. They're no better trained than you are, and probably even less well-trained. It's to shoot back with your own lawfully owned and carried firearm.