A Missouri police officer was killed during training because another officer apparently confused the standard issued sidearm with one loaded with Simunitions.

The department says that Simunition, a non-lethal plastic projectile, requires a specially-modified gun, but De Kraai and Strong were reissued their regular weapons when they briefly left the training session to get a drink from a nearby convenience store. When they returned, authorities say that Strong, apparently not realizing that he was still carrying a weapon with live ammunition, fired the deadly shot into De Kraai’s back.

At any time your gun leaves both your field of vision and actual physical possession, you must make sure to check it before doing anything else with it. And, goes without saying that any firearm’s horseplaying should not be allowed by anybody to anybody.

Lesson learned the deadly way.