If you put the volume up on the video, you hear Kyle say to his mom "Tell him not to do that again. I'm videoing this and I'm going to post it online."
IMO the video is chilling. The little girl is laying on the floor doing nothing and he grabs her and slaps her hard twice, watching her as she cries. Just watching her, no emotion. Then he apparently grabs the other baby and the video ends. If that's what he does in front of his wife while his step son is recording a video, what does he do in private?
On Facebook his profile says he has a girlfriend and two kids. Not three kids, not two kids and a great step son, but two kids. It also says he was a stay-at-home dad. So no job, just home with these babies he slaps unprovoked all day.