Not defending Baldwin, but the revolver was supposed to be loaded with dummy cartridges. He shot the photographer because he was drawing and pointing the revolver at the camera, to see what it looked like on film. The dummy cartridges were used to make it look as if the revolver was loaded.
The only way to check if the revolver was actually loaded with dummy cartridges, was to remove all six, through the loading gate, shake them hear the BB rattling inside, and then replace them through the loading gate.
Of course, Baldwin hired the armorer who was in charge of making certain there were no live cartridges in the weapons he was handed, and kept her on the job after there were two negligent discharges on set in a single day.
He swears he didn’t pull trigger. Maybe true. But single action Army Colt can be fired by pulling hammer partially back before 1st notch and letting go. Also, they can be modified for “fanning”, ie pulling hammer back any distahce and letting go will fire. My understanding. Correct me any experts out there on the SAA. Baldwin did somerhing wrong...the primer did not self detonate,