Puzzle I made

So I have a kind of a puzzle that I thought up, maybe it would qualify as a riddle or maybe a trivia question. I don’t know how hard it really is, or even if is new. I thought I might try it here though to see if… Well I must say that I have a couple of ways to go about this. I could start at the hardest(that I can think of so far) clue and then work my way down to the easiest clue, essentially giving more and more clues as it goes (but the answer to the easiest clue only lets you know what is happening, you then have to figure out what different is happening in the earlier clues) Ok I’ll do it that way.

Ok:

A man is playing competitive cards for high stakes, he sees the following sequence, and he wonders. On the next play he sees a particular card. He immediately stands up and shoots his opponent dead. Why? What is the card that he saw just before shooting him?

Ace of spades
9 of Hearts
Ace of hearts
3 of Spades
2 of Spades
Jack of Hearts
4 of Diamonds
??? of ???
Bang!

After the trial the man is in jail and he is playing cards, he sees the following sequence and says to himself “that’s odd! I wonder if [this number] is next.” It was. What is the number? Why was it odd? Sequence: Ace, 2, 7, 5, 2, 5, …..?

Another time the man sees this sequence and again is astounded. Why? Ace, 8, 4, 9, 3, 6, 8.

Years pass and the man is alone and sometimes forgetful when he sees the following sequence. Having lost most but his sense of humor, he laughs at himself and knows what he forgot to do. What did he forget and how does he know?

Ace of Spades
8 of Spades
Ace of Diamonds
6 of Diamonds
10 of Diamonds
King of Diamonds
2 of Clubs.

Community Creativity.