[Does so]

“A gun had two misfires in a closed cabin,” a source told Deadline. “They just fired loud pops – a person was just holding it in their hands and it went off.”

Two squibs—two bullets lodged in the barrel—then a real shot? That would send three projectiles—possibly accounting for the wounding.

[Cold Heart]

The one that was fired by Baldwin probably was a blank. If there were two squibs lodged in the barrel they were propelled by the blank.

Some other posting mentioned people shooting live ammo through the gun previously.

[TigersEye]

“A gun had two misfires in a closed cabin,” a source told Deadline. “They just fired loud pops – a person was just holding it in their hands and it went off.”

According to the article that was a separate incident that happened days before Baldwin shot the cinematographer and the director.