What happened is the primer ignited the wad down the bore , and the powder did not ignite -- call up the maker and demand more free shells - they will send them - the last thing they need is a safety issue
BTW -- Ive seen it happen plenty of times with duck guns shooting shells that got wet - by the time I was 8 years old we were well trained to just about punch a guy in the head to get a shot gun out of a unknowing hunters hands - If a hunter cycles out the first wet hull and fires off a second shell with the first shotcup/charge it will likely blow the gun up and worse -the typical scenario is when a good size flock of ducks flew into the spread and 4-5 guys are banging away 10-15 shells and one goes "pop" its like someone stepped on a land mine - everyone is screaming - STOP STOP STOP till someone figures out what went wrong and who has the dud
