Knowing how many more girls were killed and families destroyed by that psychopath over the years following this incident.

I’d think it would be hard not to think about the fact that maybe some alternate series of events could have led to you having a chance to stop him somehow and prevent all the future loss and suffering of others.

I’m not casting blame on the poor guy. Just knowing my personality I think I would (unfairly) carry some kind of guilt and second-guess my actions or non-actions, which would be tricky thing to balance with being grateful for what was likely divine inspiration on my own behalf.