I'd be more careful. I'm somewhat apathetic to that, and I wouldn't go rambo because it would be a pointless loss. I like planning things out, so I'd be likely to take revenge later. (Assuming that in this case they've been murdered in an alleyway without noticing me watching). I'd go bring out my log splitter axe, gloves and my old gas mask (doesn't work anymore, but whatever). I'd find out where they lived and get in as quietly as possible, then go for the head. Once I'd killed them, I think I'd desecrate the corpse in some degrading fashion as a last disrespect. Hide the corpse somewhere so they won't find it for some time, spray-paint my number plate, leave the immediate city and live in an isolated town with other isolated people. And grow a beard.
I can't believe I just wrote that...