The fellow is left-handed and was carrying his 1911 pistol inside the waistband. The pistol was holstered, but the hammer was not cocked, there was one round chambered. He withdrew the firearm, holster and all, from his waistband to change for work, and it discharged. The round went through the upper thigh/groin of his left leg and exited the back of his thigh landing in an adjacent locker. When police arrived at the scene, they had to remove the firearm from the holster to make it safe and the spent casing was still in the firearm.
What went wrong?
1. The guy lost control of (aka: dropped) the gun/holster while pulling it out of his pants.
2. He instinctively grabbed for it and sort of caught it, unfortunately pinning it against his thigh/groin (with the barrel against his leg).
3. In the process he flicked the hammer, causing the gun to discharge.
4. The gun failed to cycle, because:
---A. The guy's hand somewhat blocked the slide, and
---B. With nobody gripping the lower half of the gun, it couldn't cycle ("no-wristing" is worse than "limp-wristing"), and maybe
---C. The holster interfered with the gun's normal cycling operation (but A and B, above, would alone be enough to prevent the gun from cycling).
5. The impact of the dropping of the gun wasn't enough to jar it out of the holster.