This was just discussed on CNN.

I now think this was likely a suicide. I do not think a federal investigation is necessary. I do not think Al Sharpton needs to become involved other than to console the family. My conclusion thus far is based on:

1. The autopsy results
2. The police video of how a flexible person can get a hidden gun to their own own head
3. The marks on the right arm that support the police visual of how this could have happened.
4. His girlfriend claims he called her and said he's scared and will kill himself (if memory serves me correctly). There is a record that he made a phone call from the back of the police car.
5. The (Black) woman who says both officers were outside of the police car.
6. The man had drugs in his system that can have a certain impact on his mental state.
7. About 12% of deaths in policy custody are ruled a suicide

This could be a police cover-up but it looks more like a suicide. A suicide in police custody tends to be difficult to believe for a number of reasons including distrust of police. The investigators should have checked for gun residue at the scene. Failing to do so causes people to be skeptical.

#5 is probably the best factor going in the officers' favor. #1 would be consistent with an execution if the officer pressed the gun to the guy's head and fired.