Yeah, I think there's some topic drift on this Tom. You asked the question what would more cameras have done? I think the answer is if they provided more information about the killer, including his appearance, how he left campus, where he went, what vehicle he got into etc. that would help law-enforcement. Is it enough to save the MIT pro professor's life? I don't know, but more information is better than less information.
I completely agree that the blame for the murders falls squarely on the murderers shoulders, but we would be foolish society if we didn't take take a look at all the surrounding factors to see if there are things we can do better. That's true for this murder, it's true for every murder. We won't necessarily find things at every murder, but we should always look.