Looks fake to me.
I highly doubt anyone is stupid enough to film themselves murdering. I just don't buy that the shooter and his entourage are all OK with that. That's just way too much premeditation for a murder. One of them would have put a stop to the idea of filming.
I can however understand a bystander filming a murder scene just by coincedence. With camera phones and shit, that ain't out of the question and has happened plenty of times.