I completely agree with Threadworm (and tiredemma). The thread should be pulled and an e-mail sent with recommendations to call samaritans or CMHT).
I was talking to DH about this at breakfast (poor man another "there was this thread on mn" discussion over the weetabix). He has done some psychiatry (and sees plenty of pts with mental helath problems). There are varying levels of suicide risk, and obviously different strategies to help someone who is considering it.
I'm not sure a stream of mn posts (although they will all be sympathetic and supportive) are the best thing for someone who is suicidal. There needs to be a conversation with one person who is trained in this and who can give the best support, advice and (if appropriate) referral to other hps/agencies.