According to the released security footage, it appears that Janay may have started to whole incident between herself and Rice, an incident which cost Rice his job with the Baltimore Ravens.
A source, close to Ray Rice, proclaims that on the night of the incident, Janay had been drinking and acting out to Ray. Apparently, she had been hitting on Rice all night, but he kept his cool. Things reached a boiling point once the two entered into the elevator, as in the video (below) appears to show Janay spitting in the face of Ray.
The source goes on to say that Ray did not punch Janay (as many of us believe), but simply slapped her which caused her to hit her head against the elevator wall.
The source then says that it was a reflex and not something he thought about doing.
What many don't realize is that the two were currently working things out and working with a Pastor to get through the incident before the video was released.