This post could save your life. Read it carefully, then forward the link to your friends and family.
By all accounts, it's easy for nutcases to obtain firearms in the United States. Since there's no shortage of nutcases, the likelihood goes up every year that you might get caught in workplace gunfire.
A couple of years ago I had a conversation about with two experts on workplace violence: Don Grimme of GHR Training Solutions and criminologist Park Dietz, founder of The Threat Assessment Group. Grimme primarily addressed the issue of how to prepare for a shooting and Dietz how to react when a shooting actually is taking place.
Based on those conversations, here's how NOT to become a casualty:
Always assume that somebody who threatens to use a gun to resolve a workplace issue is both capable and willing to back up that threat with action. Workplace shooters tend to be loners with mental health issues, have a previous history of violence, or spousal abuse, and may hold extreme political views and espouse weird conspiracy theories. They talk a lot about violent acts and may share violent fantasies.
3. Don't Be Needlessly Confrontational
If somebody at your office looks likely to become violent (e.g. throwing a screaming fit, making threats), do not become belligerent yourself. Doing so can easily escalate the conflict, making violence more rather than less likely. Unless it's your specific responsibility to intervene in such situations, it's wiser and safer to withdraw from the situation and then contact either Security or the police.
4. Have a Plan
As a general rule, you should always be aware of three things about your workplace. First, the quickest way out of the building. (This is good to know anyway, because that's where you'll head if there's a fire.) Second, know the location of the nearest room that can be locked or barricaded. Finally, mentally select someplace nearby where you can hide if bullets start flying.
5. Duck and Cover
It seems a bit obvious to say this, but if you hear gunshots, hit the floor and scramble for cover. Don't assume that you'll immediately know the direction where the bullets are coming from. If there are security guards or police present, there may be crossfire. If you have armed coworkers, they may panic and shoot at anything that moves. Bystanders can and do get killed in firefights.
6. Gather Your Wits
Once you've found someplace where you're not in a potential line of fire, take a couple seconds to assess the situation. Determine the likely location of the shooter(s) and then decide what to do, based upon your options. Needless to say, this will be difficult, which is why you made a plan in Step 4. Do NOT call 911 at this point, because at this point calling attention to yourself (like by talking or having a squacking phone) is a very bad idea. I'll explain when's the right time to call 911 next.
7. Get Out and Away From the Building
Your best option for survival is to leave the building and run, in a zigzag pattern (See Step 11 below), as far away from the building as possible. Don't stop in the parking lot because you're still on the premises and therefore still in danger. If you want to help your coworkers, the best way to do so is set a good example and lead the way out of danger. When you're so far away that you're certain you're out of danger, THEN call 911.
8. Make Yourself Inaccessible
If you can't get out of the building, go to the nearest room that can be locked from the inside and/or barricaded. Once inside, lock the door and/or barricade it. Do not open the door, even if somebody outside says they are the police. It could be the shooter. Once you are secure in an inaccessible place, THEN call 911.
9. Hide (and Be Quiet)
If you can't get out of the building and can't get to an inaccessible room, then hide someplace that you're not visible. Do NOT call 911, because an important part of the concept of "hiding" is not making any noise.
10. Become Less Threatening
If somebody points a gun at you, raise your hands palm outwards and move slowly away. Research shows that this gesture makes you non-threatening and make you less likely to be a target. Many websites and videos suggest ways to disarm a shooter. Attempting to do this is an excellent way to get yourself killed.
If somebody is actually shooting a gun at you, run away in a zigzag pattern, because it's actually quite difficult to shoot something that's moving erratically. If you run in a straight line, you're presenting an easy target that (from the perspective of the shooter) is staying in one place. Keep zigging and zagging until you have gotten far, far away.
12. Play Dead
If (God forbid) you actually get shot, lie down, and do not move. With any luck, the shooter will not feel the need to walk over to you and administer a coup de grace.
I've twice been the object of work-related gun threats, so I know this stuff is for real.