I thought the same thing. I loved that part too, and would have liked to seen more. But they seemed to treat it as such a throwaway moment as the camera is pulling back.
RE: my spoiler above, after doing some reading, it seems like that was intended as a nod to the video game. I'd never heard of or seen the game, so it didn't make sense to me at the time. Still doesn't, in the context of the film, but I guess it's a wink to the video game fans.
Crazy film, really lives up to its title. This is going to really rock the subwoofer when it comes home on disc. I could actually feel it vibrating the floor of the theater, which I'd never experienced at this theater before.
I was surprised there was a fair amount of animal on human carnage...