Self-defense

Gedankenexperiment: say I see someone walking down the street in my neighborhood, randomly firing shots into houses and vehicles as he goes. I kill him. Have I committed murder, or have I defended my family? Discuss.
Oh, and I’m afraid the news that 43 American cities have passed anti-war resolutions doesn’t cut a lot of ice with me, especially after reviewing the list of cities. You are no doubt aware that what gets passed by the city council doesn’t necessarily reflect the sentiment of the city’s residents (excepting, of course, places like nuclear-free Berkeley and Ann Arbor.)