He served as a major in the military. He joined the NWMP in 1872. He was appointed an inspector of the NWMP in 1873. He saw first hand the hardships faced by the Native people as the buffalo disappeared. By 1884, he was the Superintendent of the North-West Mounted Police stationed in Fort Carlton. He warned Lieutenant-Governor Edgar Dewdney that government policies were creating unrest among the First Nations and Métis. Since he feared a repetition of the Red River Rebellion, he asked for reinforcements to be sent to the North-West. Wanting to avoid conflict, he attempted to negotiate with Louis Riel but was unsuccessful leaving the situation in a stalemate. On March 26, 1885, Crozier lead a group of approximately 100 mounted police and Prince Albert Volunteers from Fort Carlton and a seven-pounder gun to bring back provisions which were running low at Fort Carlton. These men were confronted by Gabriel Dumont and a superior force of Métis near Duck Lake, Saskatchewan; no shots were fired and the police returned to Fort Carlton. In the ensuing Battle of Duck Lake, the NWMP were routed by the Métis. The resistance that he had wanted to avoid earlier broke out. On 21 March 1885, Major Crozier received a letter from Louis Riel demanding that he surrender or Riel will "commence without delay, a war of extermination upon those who have shown themselves hostile to our rights." The retreat of the government under heavy fire tarnished the reputation of the NWMP. Crozier's role in the remainder of the rebellion was minimal, and his force largely remained at its post in Battleford, Saskatchewan. His march on Duck Lake and into an ambush stalled his career with the NWMP. Nevertheless, he was on April 1 promoted to assistant commissioner of the NWMP, a post which he held until his retirement in 1886. In 1886, after the Prime Minister, Sir John A. Macdonald, appointed a civilian commissioner instead of himself, he resigned. He spent his later years in as a merchant and banker in Oklahoma Territory, dying of a heart attack in Cushing, Oklahoma Territory on 25 February 1901. His body was brought back to Belleville, Ontario, to be buried.
