Here are 8 Signs of a Potential Dangerous Person In the Workplace. This is in no way an exhaustive list, merely a few common red flags to watch out for:
1. A Controlling Nature
This person is not the industrious take-charge type, but a true threat when it comes to controlling others. Change unravels this type of person.
2. Violent Opinions
These people tend to blame victims and are particularly interested in news about the latest school or workplace shooting, bombing, etc. It could be a red-flag if the individual often talks about, or expresses interest in, violent and odd topics.
3. Obsession With Power 
This point has some overlap with number one, but this type of individual may have a gun collection, subscriptions to ammo or paramilitary magazines, or be active on online communities for firearms. He or she might also be obsessed with law enforcement.4. Assume Others are Out to Get Them
Employees who seem hyper-vigilant, or even paranoid, may be under the impression that others are out to get them. A signal could be something as simple as a comment saying, “somebody is poisoning this coffee.” Paranoid thoughts, and expressions of those thoughts, are a red-flag for potential violent behavior in the future.

5. Frequent use of malicious references

These people are likely to say things like: “She had it coming,” or, “Karma is a great thing and will come back to bite him.”

6. A Generally Weird Personality 

They generally are the oddballs, the ones who stand out. They don’t get invited to parties coworkers throw. Although there are tons of harmless people with odd personalities, this is a potential red-flag.

7. Lifestyle is Not Health-Conscious 
Not very many of us have the discipline to live a completely health-conscious lifestyle. That is not uncommon. However, at the extreme end of the spectrum: people often smoke and/or drink, rely on pain pills all the time, are hooked on sleeping pills, eat junk-food constantly, and are the last people you’ll see at the gym performing lifts or taking a high-impact aerobics class.

8. Ongoing Anger
These types of people are frequently irate, and they often blame others for this anger. These are the people, that at some point, will reach boiling point.