I can’t count the number of times I’ve seen someone rack the slide and then drop the magazine. You drop the magazine first, THEN you rack the slide two or three times to eject any chambered round, while looking in the chamber to verify it is empty. After that, you still don’t ever point the weapon at someone and you definitely don’t pull the trigger. Regardless of what happened, this guy was a total idiot.
It’s necessary to pull the trigger in order to disassemble a Glock.