Of course, it would depend on who it was, as some people may affect me ore than others, but in the end even when it was somebody I hate or even loathe with passion, I will probably be upset. Especially when I don't know who the murderer is.
Unexpected deaths are always the ones that affects us most, and although I never lost somebody to murder, I did lose somebody to a traffic accident, and I still remember how that struck me, even though it was more than 20 years ago. The silly part is I lost people closer to me than she was, not long before that, but they have been ill for a year if not longer, I knew they were about to die. That girl in whom I lost in the traffic accident was young and beautiful, so she was smiling and so she came into a collision with a truck and died instantly on the spot. She never had the time to realize what was happening, and could be a bit of comfort...
Now that was an accident and I can say out of experience that such a thing strikes hard. In the case of murder somebody's premature death was even intentional, and if the victim is somebody you love or hate, that makes things come very very close. It can also make you realize the victim could also have been you. As long as the culprit is unidentified and their motives are not known, this can haunt you. If the culprit ever get their punishment is lesser relevant than knowing who they are and why they did it, especially when you don't know if they are not planning to do it again and if so who the next victim will be. Once you know who did it and why, only then can the question of how well punishment will comfort you (if it does at all) even come to mind. Punishment won't bring the murdered person back. Knowing who the culprit is and why they did it won't either but at least you know how much danger there is for another kill.
I don't know how I'd respond to murder. But I do know what it is if somebody is suddenly taken away from you, and I also know what trauma can do with you. Based on that, I am glad I know the address of a good psychiatrist.