Good assumption on no transfer bar.
One of three things happened:
1) The hammer was pulled back only far enough to NOT ENGAGE the half-cock sear, and that little force when the hammer was released was enough to set off a very soft primer, and Baldwin is an idiot.Can you spot the common element in all three scenarios?B) The half-cock sear notch was broken off of the trigger assembly (which can happen, and is the origin of the phrase 'don't go off half-cocked') so the hammer was pulled almost all the way back, but not far enough to engage the firing sear, and when the hammer was released the half-cock notch did not catch the falling hammer and the blow set off the primer, and Baldwin is an idiot.
III) Baldwin had the trigger pulled when he fully cocked the firearm - the hammer spring is very stiff and it is easy for a novice to inadvertently pull the trigger when squeezing his fist struggling to thumb back a very stiff hammer, and because the trigger was pulled, the half-cock sear notch was out of the way and the hammer hit the firing pin, and Baldwin is an idiot.
The wild card is the live ammo. Baldwin can be an idiot all day long, and nobody gets hurt.