Yeah, I'm pretty sure a finger was involved there

Negligent discharge.

During the training exercise, a law enforcement deputy accidentally discharged his weapon during the “un-holstering” process. The deputy sustained a gunshot wound to the leg as a result of the accidental discharge. No other persons were injured.

As a lady more eloquent than me is apt to say, "keep you booger hook off the bang switch."

H/T to David