It was an important lesson on the Blackhawk SERPA retentiom holster.
I own them,use them,like them.
You MUST develop a muscle memory/habit to keep your trigger finger straight,outside the guard as you draw.Point the finger toward the anticipated target as you depress the retention release,
If you hook your trigger finger to press the release button,you are in trouble.
As you clear the holster,with pressure on that hooked finger tip, the finger will fall into the trigger guard and engage the trigger.
Thats how the above mentioned Gentleman shot himself.
I like the SERPA holster,but its not for everyone. Its one of those "Informed Choice" things.