Perhaps one of the most embarrassing (and dangerous) avoidable situation for an officer to have is a negligent discharge (ND) of their firearm. The situation is an immediate announcement of the failure of an officer to follow safety protocols, and in some cases the result of the (ND) is far more tragic than humiliation and discipline to the officer. Recent examples of this abound.
Take for example the recent case with a BART Transit Authority officer who inadvertently discharged his sidearm and killed a suspect that was laying prone on a very busy train platform. [Ed. note: You can read more on the specific incident here. The Force Science Institute gives a very good presentation of the facts immediately surrounding the shooting.]