First, prevent suicide again. First of all, it is very lucky to save him this time, lest he embark on the road of suicide again. Therefore, he should be detained and let him calm down in the police station. At least in the police station, he can be supervised and protected by the police, so that his life safety can be best guaranteed. This is also a protective measure for citizens by the police.
Second, the purpose of maintaining environmental safety is to maintain the environmental safety of ordinary people. Because the man's behavior has caused the closure of the library and caused great panic to the people around him, the police detained him for criticism and education, making him realize how much influence he has brought to the people around him.
Third, help that person. After the police detain him, they can ask him what made him think of suicide and give him some help. Only by face-to-face communication can he understand the man's real thoughts and find the most appropriate and effective means to make him give up suicide and return to normal life.