It takes 1.5 seconds to go 21 feet from a standing stop or 2 seconds to go 42 feet from a running stop. If you shoot someone in the heart with a shotgun, they have enough oxygen to continue attacking for 6 to 14 more seconds. Anyone who regularly watches MSNBC knows it's always possible that the suspect is only charging you to give you a kiss instead of planning to take your weapon and murder you with it.