I do understand from cop's perspective, but I disagree with the way the police treated him like crap, laughed at him, and ditched him after the police had discovered his card that indicates he's deaf.
there is a part of me is that I feel that a friend, family member, caregiver, or whoever should be going with a mentally disabled adult. Yes, they do want to feel independent sometimes. Some mentally disabled adults are unpredictable and may appear to do well, but that is not always case.
A long while ago, I knew this mentally disabled deaf adult from a community college can function well, and can take a bus by himself. He carried his cards around his neck in case. He even registered for his class, but too bad, he sometimes wandered out during the class. Normally, he came to me in the middle of the class, which was a bad time, and kept talking to me nonstop. He loved to talk. I had several interpreters trying to tell him that they are trying to work, but he got upset and snapped at them. Some interpreters felt very uneasy with his behavior. You never know when he is going to throw a punch or not. I managed to ease his behaviors by talking to him like a child. I told him to visit me during the breaks, because he wanted to show me his drawings.