Getting seriously involved in changing someone else's life will incur major loss to your own. I'm speaking from several rounds of experience.
It's not to be taken lightly and it's not an automatic moral duty. I would strongly argue that your duty is to make a full bodied effort to convince their family that their own is in mortal immediate crisis. If they don't respond to that after it's clearly and emphatically communicate then it's on them. Sadly your friend is almost certainly not going to seek out professional help unless someone intimately intervenes.