Is it ethical to restrain a mental health patient outside DHBs areas?

Restraining a mental health patient in the event of acute psychosis.
The patient's presenting symptoms pose possible harm to self and others.
You are a mental health RN encountered this patient on a street with a few people with different ages also on a street.
After you ring up the police, is it ethical to restrain the patient if you see the patient approaching a person near him with menacing gaze and clutched fists.