Clayton joined the Ontario Provincial Police in April of 1959. Initially he served at Kirkland Lake and he transferred to Powassan in 1961.

Late in the evening of September 11, 1963, a bull moose suddenly appeared in the path of the cruiser that Constable Armstrong was driving during a regular patrol on Highway 11. Although Clayton swerved to avoid the animal, the ensuing collision resulted in the cruiser’s roof being crushed on the driver’s side. Although his partner incurred only minor cuts and bruises during the accident, Clayton Armstrong died of a fractured skull.

Clayton Armstrong was survived by his wife, and four children. Clayton was thirty-nine years old.