|National Suicide Prevention Lifeline|
If you live in the United States, you should know about the National Suicide Prevention Lifeline, a project of the Substance Abuse and Mental Health Services Administration (SAMHSA). The Lifeline has a page offering suggestions for how to help someone you encounter online who appears to be suicidal, and it includes information about how to report someone as potentially suicidal on Facebook, Twitter, YouTube, and other social media platforms.
I encourage you to bookmark this resource. You never know when you might need it, and it could help save a life.