Child Abuse in the Workplace

I am VERY tolerant of many things, I didn't hate the people who gay bashed me when I came out, I don't care if people say "faggot" or "fag", or "that's gay" at me. There however is ZERO tolerant to seeing a child be abused in front of me. Today in the workplace, my manager and I were providing customer service to a couple and their child. He was a cute little boy who couldn't even be 4, Steph and I noticed he had a bruise under his right eye that looked like it was beginning  to heal. That set our radar's off already, they were sketchy and had to be on something. The male was bouncing around talking gibberish while the female strolled behind him. The kid grabbed a belt from the wall and just touched it! Didn't take it down or break a thing! Just touched it. The female turned around and yelling at the child pulled her fist back and punched the child in his eye. I was so shocked because I couldn't see this coming! They bolted out of the store before we knew what to do, Steph didn't see the hitting, but I did. The kid just looked at me and started to cry, that's when the mom bolted and the dad followed seconds later.... I felt like someone kicked me in the nuts, I wanted to do something but nothing could be done, We had not gotten their names nor did they stay in the mall. Over all it makes me wonder if that boy will live long enough to reach 6 or even 5 years of age... It's people like this I honestly believe should be hurt so badly they will never forget the pain they caused others.