Can I sue for mental distress?

I had a close friend that was in a hospital for two days for leg and back pain. He was hurting so bad they admitted him and kept him on drugs but he still would not be still for MRI. They let him sign his on papers while on the medication. I know this because I asked if I needed to sign any papers and they said he did. I could not believe they were sending him home. He could not sit still. I was just visiting him. They told me he had someone coming to pick him up. I called and asked them and they said they didn't know nothing about they were supposed to. I took him. He had no one to take care of him so I stepped up. He was home 2 hours before he died and I found him which has been bothering me ever since.