Just to go back for a moment on the strength required to pull the trigger, I am not convinced a 2yo could do this. Are we certain the mom did not, in any way, have her hand near the weapon? How close to the weapon was she when it was fired?
My 3yo granddaughter could not pull the trigger. No way. Not even with both of her tiny pointing fingers inside the trigger pull and the butt of the gun against her chest. That requires a great sum of ambidexterity few young children possess.
It is surprising a child so young was able to pull the trigger and it raises the issue of a possible flaw in the design of the gun.