I do believe he hanged himself.
But it is likely he did that due to either the effects of it he was already feeling, or being informed of the diagnosis and being aware of what was in store for him as it progressed. I'm not sure how far along the disease had progressed when he died.
Chances are he noticed himself changing and falling apart and still had the ability to take his own life.
He may have already had a depression diagnosis as well.
I know my mother's whole personality changed and she wanted to suicide (totally against her character normally) many times but by the time she reached that state of mind she was not capable (physically or mentally).
I'd speculate he had been having a horrible time, got diagnosed and advised of what he was likely going to experience and said 'fuck this!' And took his own life, of which I fully understand.