This shooter clearly has a problem. Let's walk through the steps that I would take in a case like that in order to determine what was wrong with my gun.
Before you begin, review the basic rules of gun safety.
If it's a double action revolver, close the cylinder.
Cock the hammer and examine it. The reader above was shooting a Smith & Wesson Model 66, which is the same model shown above. The firing pin on this model - and on many other revolvers as well - is attached to the hammer.
If your firing pin is attached to the hammer, look closely at it and make sure the end of it is rounded, not jagged or sharp. If it's not nicely rounded, the firing pin may have broken, and if it fires a cartridge at all it may pierce the primer, allowing hot gases to spew rearward. Not good.
On many models with hammer-mounted firing pins, the firing pin is mounted loosely to the hammer. If so, don't panic. This is okay, it's meant to be that way.
If the firing pin isn't present, examine the hammer's face. With use, it may become slightly peened, and that's usually okay - but severe damage to its forward face (which hammers on the firing pin or transfer bar in order to fire a cartridge) could result in misfires.
If the firing pin is broken or doesn't look right, it's time to head down to the gunsmith's shop to confirm your diagnosis and have the pin replaced if necessary.