I need advice quickly. (See details)

Some of you may know a bit about this. I left my SO last August because of his addiction to drugs. Oxycontin. He continued to go downhill and blamed it on my leaving but really there was nothing I could do to stop it. He became homeless in January. No one will let him stay with them. I let him in to my house in February because he had literally nowhere to go, and god help me, I can’t help feeling love and pity for him. The one shelter here booted him out for missing a meeting with a social worker. I put him out last Friday after watching the whole thing start again with the lies, drugs, other women, crap with my internet connection. He went to a motel. Tonight he called me crying. He has never cried before. He says he isn’t going to make it, that there is no reason to try.
I hate to be cold blooded and I’ve abbreviated this a lot. You don’t even want to know all the horrible things he said to me about my person and my character when he left Friday and actually even before that.
Should I just let him sink or swim? Do I go and try to get him some help? This is beyond my skills and resources to fix on my own. i want him to be under professional care, but you know, he closely matches the description of malignant narcissist in another thread from today. I hate being manipulated but don’t want his death on my conscience.
Please advise me. I’m too close to this to be objective.