A story of a 40-year-old man recently accused of killing one person and injuring five at his former office can send even the most easy going office into a state of fear.
You never know if the sometimes-odd co-worker is harmless, or mentally ill with too many personal problems to count.
And while you don't want to be bothering the Human Resources Department with baseless complaints, it's better to be safe and a little too sensitive than to let things slide.
If you hear a co-worker discuss odd plans, such as saying goodbye to all of their friends, or make threats about shooting the boss because he or she didn't get a raise, then it's probably a good time to contact Human Resources or your immediate supervisor to let them deal with it.
Knowing signs of depression can help. According to the Mayo Clinic, they include loss of interest in normal daily activities, feeling sad or hopeless, crying spells for no apparent reason, irritability, difficulty making decisions and being easily annoyed, among others.
If you're up to it, you may want to talk to the possibly disgruntled or depressed worker to help ensure they don't go off the deep end and go on a shooting spree. Depending on how close you are to them, you might want to ask what's wrong, and suggest they see a doctor or counselor.
People who suddenly change their behavior might be having a mental breakdown that could lead to violence. A worker who was always nice but all of a sudden is upset with everyone may have problems that should be addressed with support and compassion before recommending a counselor.
A fascination with weapons or a preoccupation with violent events is a worrisome sign, according to a report by The Globe and Mail. A veiled threat or comment such as "Now I know why people bring guns to their work" should be taken seriously.
Security should be called if physical violence starts or if there's a verbal confrontation that looks like it could lead to physical violence.
If nothing else, report suspicious activity to your boss and Human Resources Department. It should get the ball rolling to get some help.