You can get a flamethrower in the game but that's not how you do it. This is a hard mission because it involves lots of missing. You throw grenades through the open window at the top of his apartment. You should stand on a van to reach the window with your throws. If you get your hands on a rocket launcher, that's even better. Just shoot that through the window. the problem is, once you FINALLY get that then you have to chase after the guy and mess up his car. Anyway, that's how ya do it.
