How do you know if your case is medical malpractice or wrongful death?

They also gave him a prescription for it. He walked a block from the hospital and fell down and stopped breathing. He was given mouth to mouth by a stand byer. The ambulance arrived a while after he fell. He was takin back to the same hospital where they said he would be fine. He then slipped into a coma and lost his bowels everywhere. They scanned his brain and ran medicine through him. They said he was brain dead when I arrived. Then they said there was a chance he would awake. Then it went back to he would never awake. When the autopsy was completed the medical examiner told me his death was undetermined. They found loritab in his system but said nothing of his other medication he was on. My father also had a clogged artery which he had surgery on before. The hospital turned him away and said they would not operate on it until it was 90% blocked. When he fell down that day it was 90% blocked. Im not sure if I have a case or even how to go about it.