OK, I'll put in my 2 cents. Question, "is it possible for a 2 year and 9 month old child to pull a Glock trigger?'. Answer, yes, it's absolutely possible. Is it probable, very, very, doubtful... My son was pretty coordinated as a 2 1/2 year old, and I know he would not have been able to do it, no way...
I would be absolutely shocked if a 2 1/2 year old could coordinate getting a grip on the gun, in a manner that could get off a shot, let alone the odds of the (one) shot hitting a fatal mark. Most people have a natural tendency to move (quickly) aside/away from the muzzle of a gun that is pointed in their direction. Then, of course we've got the custody hearing, and 'visit' thing going on... That's a whole lot of questionable stuff coming together, all at once!
The limited facts that I've heard, just don't seem to add up in the father's favor. Seems like the police are pretty skeptical, as well, if they are not allowing the father to be with the grief-stricken son.
Either way, a horrible tragedy. You'd like to think that the truth will come out, and justice will prevail, but you never know! Of course, let's not forget about our justice system's presumption of innocence standard, everyone is innocent until proven guilty.