I think it's from a thriller but it could be horror.
There's someone hurt, or unable to move, and someone with a knife. The person with the knife isn't normal, i think it's something mental like a handicap or something. And the defenseless person is nodding no but the other person stabs him or her. First he stabs him/her very slowly like he's doubtful, but then he seems to enjoy it and stabs him/her a lot.