All persons appointed under the provisions of this chapter as patrolmen or special police shall be under the direction and supervision of the chief of police. They shall be subject to the orders of the chief of police, except in cases otherwise provided by ordinance. It shall be their duty to cause the public peace to be preserved and to see that all laws and ordinances are enforced within the city limits. When violations of any law or ordinance shall be reported to them or come to their knowledge, they shall cause the required complaint to be made and see that all possible evidence is procured for the successful prosecution of the offenders. (1960 Code, Sec. 1-804)