Sometimes when we fear something we sabotage it ourselves to be in control of it happening. It is quite possible he was sick with grief in advance of what he felt was going to be a coming failure in the relationship owing to his depression. Thus he may have chosen to end it before the worse happened. This is not unusual for people with anxiety and depression. I have sabotaged more than one relationship and job before they had a chance to fail. It's a nature of the beast.