I somewhat recently attended the funeral of a friend of mine whose husband committed suicide. She was pregnant. I was very glad to hear that the homily was NOT a bunch of nice platitudes merely to comfort HIS family, but included a stark, vivid commentary on how gravely sinful his decision was, and how he had so badly wronged this young woman and their child.
He was blunt when he called it gravely sinful, and offered no opportunity for repentance. He reminded everyone that those who die in mortal sin are not saved. Yet Christians of good conscience could still pray for his soul, because we do not know for sure he is in Hell. the gravity of a sin is not the only characteristic of mortal sin; it must be also be an expression of one’s free will. The young man had sought out help, had sinned and sought redemption. “We must not brush aside the cruelty and sinfulness of his act; we must also not judge his soul, for none of us knows what the state of his mind was when he died. As hurt as we are — and many among us are deeply hurt, a few beyond measure — we must also offer forgiveness.”
Depression is a real mental illness. Saying “Christ is the cure for any mental disorder” is as naive as saying “Christ is the cure for any disease.” Christians die of cancer. And they get depression. And people who judge them as being bad Christians because they get depression only slander the name of Christianity. Robin Williams made a terrible decision. But it was a decision made under temptations you’ve never felt. Judge his action: it was terribly evil. Do not judge the man.
Yeah, sometimes it's hard for us to tell for sure.