Should I call the cops or is it nothing?

I was pulling out of my mall parking lot just now and saw a fairly large group of uni age people standing around in the parking lot.

1 of them was on his hands and knees and it didn't look voluntary to me (I don't think it was because he was drunk either) [I could be wrong]

Is this a let it be situation or call the cops just in case situation

Edit:
Since it's been a while and I was too indecisive, it is too late for the cops.
Hopefully nothing bad happened, and the mall has security cameras and a guard so if something did they'll have a way to catch them I guess.