'Before he even really thinks about what he's doing' means that he still has reaction times. Sorry, but he isn't going fast enough to pulverize Ocelot before he gets braincapped. It takes a lot to kill a human instantly, but a shot to the head kills most everything in a moment.
--
Sburbopolis, Homestuck RPG: http://www.gamefaqs.com/boards/8-gamefaqs-contests/60981373