Could you tell me what happens when a suicidal person get admitted involuntarily into the psychiatric ward?

They live. Someone is admitted involuntarily when a mental health professional or law enforcement official decides the are in imminent danger of killing themselves. Each state has slightly different laws, but this usually means an observation period of 72 hours. During this time medication can only be used if the patient is in immediate risk without patient consent.
Safety first. 1) change into hospital pj's and get rid of all potentially dangerous items (e.g. Belts, shoelaces, soda cans). 2) suicide precautions: range from 1:1 observation where a staff member remains always at your side to every 5, 10, or 15 minute checks by staff. 3) evaluation by a psychiatrist to determine the type of treatment indicated (e.g. Antidepressant medication, psychotherapy, electroshock).