In this video we see what is known as a "hang fire." Hang fire refers to an unexpected delay between the triggering of a firearm and the ignition of the propellant. This failure was common in firearm actions that relied on open primer pans, due to the poor or inconsistent quality of the powder.
Obviously, the most important thing here is to NEVER EVER look down the barrel of a firearm. This gentleman is lucky to be alive!