Mandle, did you hit re-submit??? 
No, I changed the part that didn't fit the facts

But it still doesn't fit the facts now that I look again so please ignore it and:
Here's my new guess(es) at the solution:
VERSION #1They were playing a game where they each draw a card and whoever gets a certain card (for example an Ace) must shoot themself.
Mr. A shuffled the deck and spread the cards out on the table
Everyone drew a card
Mr. B looked at his card: The ace of spades
Mr. B shot himself
Mr. C looked at his card, but it was also the ace of spades
Realizing Mr. A was using a rigged deck that contained only aces Mr. C choked Mr. A to death
Mr. C died from a heart attack caused by all the excitement and exertion
VERSION #2They were playing a game where they each draw a card and whoever gets a certain card (for example an Ace) must shoot themself.
Mr. A shuffled the deck and spread the cards out on the table
Everyone drew a card
Mr. B looked at his card: An ace
Mr. B shot himself
Mr. C looked at his card, but it was also an ace
Suspecting Mr. A was using a rigged deck that contained only aces Mr. C choked Mr. A to death
After killing Mr. A, Mr C. checked the rest of the cards and found that it was actually a normal deck
Mr. C died from a heart attack brought on by the shock of killing Mr. A in cold blood
(Or something like that... Something about one of them getting busted for cheating feels right...)
So also a question in the likely event my solution is not right:
Did one of the men get busted for cheating at the game?