Maybe the enterprise of saving lives shouldn't be put entirely on the police? Obviously they have a role to play, but when we are talking about prevention, other institutions also have a huge role to play.
For example, many killings are the result of mental health problems that are going untreated. Part of the problem there is that the necessary care can be expensive. So....let's do something about that. What does the government-funded health care landscape look like these days? And what about educational grants (NOT LOANS) for mental health practitioners?
There is also still a strong social stigma against seeking mental health. Nobody is embarrassed to say something like "My arm was broke so I went to see the doctor," but the moment someone utters the phrase "mental health" everyone thinks of him as crazy, weak, and pathetic. This is ridiculous, and we need to put more social engineering to the task of fixing that (for example, a lot more television and movies can include scenes and dialogue implicating that the popular characters are seeing mental health professionals...and the attitude is that this is just a given that normal people do this sort of thing on a routine basis).
There is quite a lot that can be done, and the police can't be left alone to do it all.
Keep Sound Minds is trying to reduce the stigma of mental health issues and work toward policies that help people get help before damage is done.