Why was the gardener running at Chris?
It makes for an unsettling and intimidating moment, but I'm thinking that because the gardener was possessed by the old man in the promotional video that Chris sees later, maybe the old man just saw a random black guy in his yard that he had to subdue for the "process", and ran full pelt towards him to rugby-tackle him to do so. Only when he saw it was Chris at the last second did he veer away, thinking "nope, not this one, we've got him sorted already". Maybe it was the old man who kidnapped the black man at the beginning of the movie?