It is a good question. It is very hard to fire a Glock without pressing the trigger, so some might question the chance of Glocks ending up in these numbers, claiming that if the trigger is pressed, it is not really an accident.
However, I recall at least one case where the pull on a coat waistband got into a Glock trigger guard; when the officer tried to holster the pistol, it accidentally discharged, but no one was killed.
Most fatal firearms accidents today occur among a subset of young males who are notoriously unconcerned with risk or responsibility.
As an example, I know of at least three fatal firearms "accidents" where the people involved were drinking, one of them put a beer can (or equivalent) on their head, and said: Shoot this can off of my head!
A lot of people would say that the above behavior wasn't really an accident, but negligence. Still most fatal firearm "accidents" today involve that level of irresponsible behavior.