Before we get into this, it's important to note that nobody's dead, so this accident isn't tragic – just ridiculous.
23-year-old Sam Vestey of Columbus was appearing in an amateur fan film about Deadpool, the Merc with a Mouth, with his friends Michael Galusick (starring as Deadpool) and Casey May, and they were using a real gun, beknownst to them, filled with real bullets, unbeknownst to them, as a prop. As you might expect, it accidentally slipped and shot Vestey in the leg – or so went the initial report.
Vestey appears to have commented on Gamma Squad with a clarification of the story, saying it wasn't a real bullet in the chamber of the shotgun they were using, but a blank round they didn't know was in the gun that was fired at point-blank range at his leg after it slipped. Contrary to the general reports of stupidity around the story, Vestey apparently stresses that it was "a true freak accident, and everyone there that day acted to the best of their ability, and was never treating the weapon as anything less than a deadly weapon." Although he also says that "the gun was checked multiple times prior to shooting that it was unloaded" and that some mystery person slipped a blank into the gun while they were using it in West Virginia while shooting a horror film. That would seem to indicate that the last time anyone checked it was before their entire trip, and not multiple times on the day of the incident.
Whatever the truth is, the fact that some goofballs making a little movie about Deadpool, who trades on crazy, over-the-top, devil-may-care gunplay, manage to get someone shot on set is unfortunate, but weirdly appropriate.
Here's a sampling of the finished product of Galusick's fan-films, in case you're curious.