What caused Hitler to kill himself?

Answer 1

I suppose the most direct cause was the fear of being captured by the Russians. In retrospect the defeat, total defeat of Germany seems to be plainly obvious once the D Day landings are securely ashore in Normandy. The Russian advances in the East are on such a broad front that the scope for strategic manoevre is unstoppable: The Germans have run out of materials & manpower to maintain the offensive, despite Arnhem & The Battle of the Bulge. It is suggested the Allied demand for unconditional surrender delays the end of the war in Europe, making it more difficult to depose Hitler before he takes his own life.

Answer 2

Hitler most likely shot himself, as well as his 'sweetheart' killed herself because at the time, that probably seemed like a better alternative than to be in the hands of his captors when he was finally caught. He knew that they would show him no mercy, and probably do what he did to the Jews. He did it to end his life without suffering afterwards.