You would be kind of at the mercy of your prop people. You could check the pistol, but from the back, a blank is going to look the same as a live round. You could say he shouldn’t have been pointing it at anyone, but maybe he wasn’t. They don’t point pistols firing blanks at people because they’ve learned bad things can happen even with blanks. But an actual bullet goes a lot farther than blank. For all we know they could have been shooting and these people were twenty yards away doing something else.