SERPA holsters are not, by themselves, unsafe.
SERPA holsters do, in fact, place the shooter's finger above the trigger guard, indexed along the frame.
When used properly.
As you can see in the pic, the actual retention "hook" retains the gun by holding against the trigger guard. That would be the little tab you see to the left.
As you can also see, the retention release tab actuated by the trigger finger, is indeed located above the trigger guard. When depressed by a flat trigger finger at the beginning of a draw, the trigger finger stays indexed along the frame just like it's supposed to. Until you move your finger.
Those who say that this was caused by a poor holster design are either ignorant of the proper operation/design of the holster, or are simply against the brand name because of some other type of bias. It is not an unsafe design, it has simply been used improperly by a larger number of people than other holsters.
EDIT: Pretty much every different breed of holster requires a slightly different muscle memory set. I'm sure we can all agree on this. Just because something is different, doesn't mean it's bad.
When one does not use equipment properly, bad things may happen.
I used SERPA holsters all over Alaska in all types of terrain, rocky, sandy, wet, salty, snowy, icy, muddy, gritty, etc... Never one issue. Had the gun/holster on me wherever I went. Never failed to draw during bear encounters, and always worked properly.
Glad the guy is okay.