If you have knowledge of a person who talks of plans for self harm (especially including, but not limited to, self-deletion), and they articulate a plan or plans, you have sufficient reason for calling law enforcement. 

In many states, law enforcement will contact and interview such people, and if law enforcement finds that the person has a plan, the officers can place a psych hold on the person. This varies from state to state as to length of time, necessary reasons/evidence, and where the person is held.