"If you don't know the people dying... why should you care about them?"
Probably because subconsciously we want to figure the odds of something similar happening closer to us. As long as we can blow it off as
"it'll never happen to me" then our level of concern drops. But if it's something totally unexpected that could pop up anywhere (deranged shooter, airplane takes out a building), then we start screaming about how local authorities need to DO SOMETHING to keep it from happening to us. Typically that "something" is a kneejerk reaction that wasn't well thought out, won't really solve the problem, and just gives people a feel-good illusion of increased safety.
(but the Department of Homeland Security is a different thread 
)