He immediately went into action by initiating a sweep of Manhattan to clear out the countless street gangs, many of whose origins could be traced to the 1860s and earlier, then active in the city.

[2] In the aftermath of a gun battle that lasted nearly a half an hour in front of Arlington Hall, during which court clerk Frederick Strauss was shot and killed, Mayor Mitchell personally ordered McKay to "suppress the gangs at all costs".

McKay immediately suspended the local precinct captain in which the battle occurred and sent in Deputy Commissioner George Samuel Dougherty with a squad of detectives who arrested over 100 gang members within twenty-four hours.

The situation created a serious problem by delaying the city legal system when many of these cases the charges would be dropped for lack of evidence.

[2] McKay eventually left the police force after five months, his successor Arthur Woods carrying on his campaign against the underworld which ended in 1916, taking a position as vice president of J.G.

Upon the United States' entry into World War I, McKay returned to military service as a colonel and was assigned as director of artillery ammunition production in March 1918.