The video shows another boy slowly approach and try to calmly pull the officers grip on the first boy. He is not successful. 

At this point, I wonder what these boys are supposed to do when they see a grown man dragging a child, who is asking to be released, from the sidewalk toward his house? Or even what are they supposed to do when a grown man starts shouting obscenities at a girl? If this situation had turned out that this man had harmed the girl or the boy, and others had stood and done nothing to stop it, these armchair critics may have complained that they had no moral conscience to stand idly by and let it happen.

Regardless, after repeated efforts to ask for release and one attempt to calmly pry the boy free, a third boys charges and puts his shoulder into the man like a football player throwing a blocking, apparently attempting to break the other boy free. He retreats immediately. No punches, or kicks. The grown man hold on and retreats, dragging the boy into the bushes.