I guess we will never know the entire truth, only the sad end result. I'm not entirely sure how the 20/x vision system works (seems to be an american thing?), but afaik 20/20 is normal while 20/200 is legally blind. He seems to be left with 20/25 - no idea how that compares to population average etc.
I'm convinced this is not the result of an accidental mirror hit though. You can try with a <5 mW (pref 1 mW) laser if you want to... just wave it around a in a laser-show like fashion in proximity to a mirror. Hitting yourself in the eye by accident is easy doing that, but its gonna be a quick sweep across the eye, much faster than the blink reflex can save you.
I suppose we should make a distinction between accident and incident: I'd call it an accident if someone is playing with a laser, shines out a window and hits himself in the face with a reflection. Obviously not a smart thing to do, but very different from purposely shining yourself in the eye for a prolongued period of time - using a mirror or not.