It turns out that the gun really was in the holster when it discharged:
"Lehn said as two IMPD officers stood up to leave - their seats very close together - the one officer's holster somehow became entangled with either keys or a radio antenna hanging from the other officer's equipment belt.
He said when the one officer stood up, the keys or antenna got caught in the holster and pulled on the trigger, discharging the gun. The bullet struck the deputy sitting behind the officer in her knee."How could this happen? After all, "A holstered gun is a safe gun" is practically an axiom.
Not always, though. See, Not All Holsters Are Like That. Some holsters require more precaution than others.
The holster in question was most likely for a pistol with a weapon-mounted light, and because the holster mouth on those has to flare widely enough to accept the WML, the trigger is shielded, but something small enough can still be inserted in there.
Pictured is a Bawidamann Gotham IWB with a Glock 34 wearing a Surefire X300U. An adult male probably isn't going to get his trigger finger in there at an angle that could pull the trigger, but a smaller finger might.
Proceed accordingly.
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