Doesn’t sound like an accident to me either.
I didn’t notice if there was a magazine inserted.
The procedure for clearing such a pistol is:
Remove the mag,
Pull back the slide & check the chamber,
Let the slide go forward,
Point it in a ‘safe’ diection and then pull the trigger.
Ì he skipped a step. . .
umm could be....removed the clip but not the one in the chamber?