At first I thought this cutout was some kind of a joke, but it's real: A guy kept firing multiple times after his Smith & Wesson .357 Magnum revolver got blocked with a bullet. Gunslingers call these squibs, and apparently they can be quite dangerous. The guy who fired these was really lucky.
According to Redditor NitsujTPU:
There are two main causes of squib rounds:
1) Inadequate powder put into the load. Many people use reloaded ammunition to save money, or to customize their loads (this is especially popular among competitive rifle shooters, because they will tune the way that they make the bullet to their specific gun).
2) No gunpowder in the load. A cartridge (the thing that goes into a gun: a bullet, primer, casing, and charge), has two explosives in it: the charge, which propels the bullet out of the gun, and the primer, which sets off the charge's explosion. If there's no charge, the explosion from the primer can send the bullet just far enough into the barrel to jam the gun.
The guy was really lucky because his gun didn't explode:
Yes, this is a big danger, but it's a bigger danger in certain kinds of guns. In a blowback action pistol, the gasses would be vented out the back of the gun and into the shooter's face. There's little danger of the gun blowing up, but the sensation could be quite unpleasant and debris flying out the back of the gun could cause an injury. It would not be the same as getting shot. The bullet gets all of its get-up-and-go from the trip down the barrel, so if the casing flew out backwards, it would be going at a relatively low (by relation to a bullet) velocity. (You still wouldn't be happy about it.)
In a bolt gun or a gas-operated gun with a rotating bolt (such as the AR-15), the action is intended to be pretty close to air-tight during the phase of operation when the explosion occurs. This can cause the barrel to burst or parts to fly off of the bolt or bolt carrier group. That's pretty darned dangerous in the worst case, because all of those parts are right next to your face when you're shooting, and your arm is kind of wrapped up in there. Blown barrels can cause severe injuries, though I've never heard of it happening on a properly-smithed, properly-operated gun. In the rare cases that I've heard of first-hand, nobody was injured severely. That said, taking a look at the gun after, I'm sure that this has been more a matter of luck than anything else.