Maybe he didn't hear the "pffft" on the trigger pull before.
Have seen several guns/barrels destroyed by firing after a squib put a bullet in the barrel, all due to careless reloading.
Several .45s (all 1911s) and two Browning high power (same shooter same gun!).
The .45s blew the magazine and remaining rounds out the bottom of the gun splitting the grips. Where a double charge was involved the unsupported part of the case blew, destroying the magazine and grips but the barrel/gun was not.
Injuries to the shooter were mostly stinging of the hand and perhaps a few splinters.
With the Browning high power ans its' supported chamber the barrel was destroyed (twice, separate incidents) splitting lengthwise but otherwise no damage to the gun or the shooter. Each time the cause was a squib putting a bullet in the barrel and the shooter racking the slide as if to clear a malfunction then firing again before the RO could stop him.
The one suib I experienced was due to a round without powder and it did put the bullet (200gr swc .45) up the barrel, happened during a match but I heard the 'Pfffft' and knew instantly what had occurred.
In hindsight there is a lot to be said for using a pistol with a steel frame. A polymer frame gun might have much different results. Hands/face full of plastic schrapnel is not my idea of fun.
That said, careful reloading eliminates any such problems.