A leaked video shows a group of probation officers brutally beating a teen inside a California detention center.The video, which was leaked to Witness LA by someone from inside the probation department, shows four probation officers beating the teen, while a supervisor looks on.According to Witness LA, the video was recorded inside Barry J. Nidorf Juvenile Hall, located in Sylmar, California.The video has no sound, but it does show the 17-year-old talking to the supervisor moments before the attack. The footage does not show the teen threatening the officer in any way.A second officer rushes in from the hallway and begins hitting the teen from behind. As more officers rush into the room, the teenager is tackled and thrown to onto the cell s cot.The officers pile on top of him. Video shows them punching the kid over and over again. At this point he is on his stomach, but his head and upper body are no longer on the cot.The supervisor remains standing near the doorway, watching the entire incident unfold.According to Witness LA:The supervisor, who appeared to be overseeing the beating, was reportedly the facility s  Officer of the Day  meaning, he was like a watch commander at a police or sheriff s station. He was the guy in charge of the whole place.About a minute into the beating another uniformed officer can be seen entering the cell. He watches for a few brief seconds, then exits the room, leaving the officers to continue beating the minor who is in their charge.Witness LA reports that this person was a second supervisor.The beating lasts nearly two minutes.After being seen briefly by a nurse, the teenager was taken to a hospital where he was treated for multiple injuries, including bruising, black eyes, swelling and abrasions. He was also treated for a sprain.Witness LA did not release the entire video. A portion of it was published by ABC 7. Watch the footage below, via YouTube. Image credit: Video screen capture via ABC 7 News on YouTube