ST. LOUIS COUNTY, Mo. (KMOX) -  The video shows a man wearing sunglasses and head-to-toe black clothing, carrying a backpack, walk into a busy office lobby and without saying a word shoot a security guard and a woman to death at close range.

As others in the office start screaming and diving for cover, a deep voice intones “If you’re ever to find yourself in the middle of an active-shooter event, your survival may depend on whether or not you have a plan”.

It’s a six minute long video produced by the city of Houston but recently linked to the homepage for the St. Louis County police department.

“It really is a shame that (law enforcers) have had to do something like this,” county police chief Tim Fitch tells KMOX News. “But we do think it’s important to get this out there because this is the world that we live in and people need to have all of the information available to them to help survive something like this.”

He references the recent mass killings in Colorado and Wisconsin, adding that knowing what to do can save precious seconds when a shooter attacks.

The producers of the video recommend three options for those caught up in a shooting — “Run, Hide or Fight”.

“The first option, obviously, is to run,” Fitch says. “If it’s safe, get out. If you can’t get out then the best thing to do is to hide, be very quiet.”

The “Run. Hide. Fight” video ends with a group of employees trapped in a break room taking up improvised arms — a chair, a fire extinguisher, a belt, a pot of coffee — and getting ready to attack the shooter once he approaches them.

“As a last resort if your life is at risk…fight!,” suggests the video’s narrator. “Act with aggression and commit to taking the shooter down. No matter what.”