KatiMo:

My suggestion is to run for the hills unless this person is willing to get ongoing therapy.  My heart goes out to anyone dealing with depression, but my heart goes out even more to that person’s loved ones.  I do not blame the depressed person for his or her actions; something else inside their mind is talking, but understand dealing with that person will be all-consuming, demoralizing and heartbreaking.  Leaving may well be the hardest thing you ever do, but you have to establish boundaries this person will meet.