Lets consider something. John McCain died this weekend. No sign of previous illness from his tumor, was working right up to the end.
I work in the medical world. Chemo isn't like life support, you don't stop taking it and die the next day. It takes a LONG fucking time for someone to die unless they were literally at deaths doorstep, upon which the chemo would kill you first. Chemo isn't a miracle 'feel good' drug, it's some kind of poison that usually kills cancer, slightly faster, then it kills you.
This man likely killed himself on Friday, was announced dead on Saturday.