Skill 58: Barricade an inward-opening door If you can't escape an active shooter, create a barrier between yourself and danger. Buy time and stay alive. (Daniel Woolfolk and Lars Schwetje/Staff) Learn to barricade an inward opening door in the event your office or home falls victim to an active shooter. Clint Emerson is a Navy SEAL (Ret.) and the author of 100 Deadly Skills.