Legal Conumdrum/Riddle

Is the case a suicide or a murder?

Yes.

Hope that helps.

At the moment the future jumper loaded the gun, he was guilty of attempted murder (of the other man's wife). He took a substantial step with the intent to cause her death.

The man who shot the jumper is not guilty of murder. He did not intentionally cause the death of another. In my opinion, he's not even guilty of manslaughter, which requires an awareness of the risk.

The cause of the jumper's death is neither suicide nor murder. (I'm not falling into the trap that wants to direct my attention to non-relevant intervening cause arguments.)

This one is actually pretty easy.

Presuming that the coroner can determine that the cause of death was the gunshot rather than the fall, and presuming that this event occurred in Illinois, I'd say that the husband should be guilty of involuntary manslaughter. The relevant language in the criminal code reads:

The husband's act of shooting a gun at his wife was such that it was likely to cause death or great bodily harm. Granted, the husband would argue that he was aiming at his wife rather than the falling suicide, but the statute only says that his actions must be likely to cause death or great bodily harm to some individual, not necessarily the person he was attempting to kill. And it will avail him little were he to claim that he thought the gun was unloaded. It was his misfortune that the gun was loaded, and it was his duty to make sure it wasn't. Indeed, aiming a gun at someone and pulling the trigger on the assumption that it is unloaded is the height of recklessness, which completes the requirements for the crime.

I'd add that the husband would also be guilty of aggravated assault, but that doesn't seem to have been an issue for the writer of the hypothetical.