Very well, I mean, it doesn't really say how long the two knew each other or how well. I am not a big believer in rushing into serious relationships and I am also not into drama dating, even when I was single. Don't get me wrong, I did have similar situations happen but I always tried to pay attention to how people acted. It's very unlikely that a person who is engaged in such a volatile situation is able to hide it. There will always be signs if you watch for them. In a situation like this, I have to believe that a person picks up on them unless they just don't want to. If that's the case, then it is on them for ignoring those signs so that would be a little bit of A, to an extent.
It's certainly on the shooter because who goes out and shoots a person for simply driving up to your Ex's house? So that would be some C mixed in.
I'd have to think that some of this is on her as well because if she knows that her Cra-cra Ex Husband is capable of something like that, and how could she not, then she has no business allowing a relationship to extend to where it sounds like this one has gotten to, without giving some kind of warning. I mean, if this has been going on for years, and it would have to have been because the example states that the relationship happend some years ago, then it's definitely on her as well. People that unbalanced don't just ignore their Ex Wives personal lives for years and then all of a sudden just drive over with a gun and kill somebody. That type of behavior has to have gone on for some time and if that's the case, then she should have gotten the Law involved. She should have filed a restraining order every time he did some stupid thing and he should have been in jail by now. Unless, she did something to allow it to continue. Unless, she wasn't really done with that relationship and facilitated the situation by being dishonest. The situation is too random for it to just be a coincidence. How does an Ex drive up, after years of not being together, with a gun in his hand, ready to shoot you? That just doesn't track so yeah, B as well.
Now, if she in fact, did explain it all and the person who got shot just ignored it, then that's on him. He knew the situation and decided to go ahead and play it out. That could be an A situation.
If, by some strange cosmic imbalance, the situation just happened to be that an Ex from several years ago just somehow went crazy and lost their mind, bought a gun, happened to show up after all these years of not seeing the women at exactly the time this guy showed up to pick her up for the date and got himself shot, then there has to be an E for that one because that would have to be filed under some kind of twisted fate. The Gods at play so all you do right then is smile to yourself and figure it was never really in anybodies control to begin with. That would be E. I don't really believe in that scenario but if that's how you are saying it happened, then that's what it would be.
Personally, I can see how it could be A, B and C, all at the same time. I even think that's probably most likely in that situation.