How would you react to this situation as a bystander with a CCW?

I saw this on the news and began to think about how I would handle this situation if I happened to see a situation like this. Curious how others would handle it. This Youtube clip is the full-length video of the incident and the best one I could find. https://www.youtube.com/watch?v=GUSDuIRBUyE via /r/CCW http://bit.ly/2Tju0aa