It is the duty of the police department to apprehend and arrest on view or on warrant and bring to justice all violators of the ordinances of the city and the charter; to suppress all riots, affrays, and unlawful assemblies which may come to their knowledge, and generally to keep the peace; to serve all warrants, writs, executions, and other processes properly directed and delivered to them; to apprehend and arrest persons violating federal or state law as provided by law, and to turn them over to proper authorities; and in all respects to perform all duties pertaining to the offices of police officers. (Prior code § 1-10)