People who threaten suicide repeatedly do so to get other peoples attention and they know it works. So they keep doing it.
That's why you don't go over there or get involved in any way other than making the call to 911. Just because they threaten repeatedly doesn't mean they won't eventually do it. 911 dispatchers have a job to do and if they get tired of the same people reporting suicide threats, maybe they should get in another line of work.