Browning 9mm. So he was shooting a Hi-Power in a weak hand drill. Like the 1911, the Hi-Power has a manual safety on the left side of the receiver, set up so the thumb can sweep it off when it's time to get serious.
If you shoot right-handed.
The Hi-Power thumb safety could be awkward to manipulate with the left hand if firing one-handed, but it's difficult to envision how the guy got the gun turned around far enough to shoot himself.
(Not my pistol. I borrowed the image from a Hi-Power thread on the M1911.ORG forum.)