Can and how do I get surveillance footage of an incident at an in-patient facility?

My 15-year-old brother, who suffers from bipolar had just signed himself into an in-patient facility because he cut himself and said he wanted to see how it felt so he was prepared for when he cuts his throat. My mom got him to agree to go to the hospital. He got scared before going in and ran but the cops found him and he went willingly and quietly back to the hospital where he signed himself in. A nurse tried to talk to him but he said he needed to calm down first before he was willing to speak. She kept pushing him till he finally told her he didn't want to talk. She got a cop who spoke very aggressively and put a hand on my brother's shoulder. My brother pushed his hand off and said don't touch me and the cop started screaming at him saying he was going to arrest him and my brother got mad and flipped one of those toddler tables that kids color at over and they tackled him to the ground and arrested him. When they were bringing him outside my brother told the cop that he was twisting his arm too hard and to let go because he was hurting him and the cop told him to shut up and my brother then spat in his face so the cop threw him on the ground and spat at him and repeatedly punched him in the back of the head. When my mom went to go see him in jail his head is swollen and his ears and eye is bruised. They had a, not sure what it is called, pre-hearing and the cop lied and said that my brother closed fist punched him in the face instead of pushing his hand off his shoulder and didn't even mention the table incident so we want footage to prove what had actually happened because cops are supposed to know how to deal with kids both suicidal and mentally ill. There were clear signs that you could see in my brother proving that he was going to explode and both the nurses and cop just escalated it. The cop also had no right to use that much force on my brother. They are trying to charge him with two felonies and a misdemeanor.