They can protect him from himself on an immediate basis, and hold him for 72 hours, after that it would be up to a judge to hold him longer. I know in my own experience, when I had hurt myself and a neighbor reported it (not knowing what was going on), I was taken into protective custody because I was an obvious threat to myself. I convinced them that I wasn't actively suicical, and they let me out after an evaluation. And I sought help after that. Maybe having someone care enough to intervene would be enough of a jolt to get him to take advantage of help. But maybe not too. And maybe they would be able to hold him long enough that he could see the need for change. You can only do what is within your ability though. Keep yourself safe, and remember that you can't be responsible for his decisions, and he's only going to get better when it's his idea.