New York Consolidated Laws, Criminal Procedure Law - CPL § 140.35 Arrest without a warrant;  by person acting other than as a police officer or a peace officer;  when and how made

1. A person may arrest another person for an offense pursuant to section 140.30 at any hour of any day or night.

2. Such person must inform the person whom he is arresting of the reason for such arrest unless he encounters physical resistance, flight or other factors rendering such procedure impractical.

3. In order to effect such an arrest, such person may use such physical force as is justifiable pursuant to subdivision four of section 35.30 of the penal law.