I can see the parents side, being a parent I would hate to lose my girls. But I can also see the point of a 'kid' who had already gotten in trouble 5 times!! throwing rocks (and you know we are not talking pebbles, or small gravel, he was probably throwing the biggest he could find, intentionally trying to hurt the agent). I don't think the kid was blameless. Yes less force might have been a good idea. But really in that situation are you thinking 'oh this little kid is someone's baby let me be gentle?' No you are being attacked by a group of people throwing rocks at you. (In Biblical times, they stoned people to death!!) I would have to say not being a sinner and forced to stand there and allow the stoning, I would do what I could to make it stop. If I had a weapon I would use it. Maybe when the kid saw the agent pull the gun, he could have said 'oh shit this guy is serious!!'  Obviously being in that area with people who were trying to get across, he probably didn't have the best of intentions. I think its a little deeper then being in the wrong place at the wrong time.

  "Facts are meaningless... They can be used to prove anything!" ~ Homer Simpson