I tried watching the video via link provided, and it was a 4+ minute video seemingly played at 1/2 speed, eg. the audio was all distorted. At about 2:15 left to play, the picture froze while the distorted audio kept playing. So I watched the video on another site, where it was a 2 minute video that played at normal speed. I'm not sure if this is all due to my phone, or how the video actually is.
I mention this all because unless there was a lot more of the video that I didn't see on either site, all I can say is holy over-reactions Batman! The kid didn't receive any broken bones in the 2+ minutes of video that I watched, not even close. He started screaming for effect as soon as anyone touched him, and also because I'm sure he was scared ****less too. The adults were trying to scare/terrorize/teach a lesson to the kid (I cannot say which because I don't speak the language spoken in the video), not seriously hurt him. That much is obvious. Schoolyard fights at that age are a lot more vicious. If it was indeed for being caught stealing, kid got off pretty light. At that age, had I been caught stealing, my own parents would have done worse to me.
Again, this is all provided that I did see the entire video, and not miss a severe beating that came later. My phone showed the same video from a couple of sites, so I do believe I saw it in its entirety.