He enlisted into the Royal Naval Reserve and was sent to H.M.S. Victory, the Naval Training Depot at Portsmouth for his initial training. While he was at Portsmouth he contracted measles and after complications had set in, he died on the 15 of September 1918 aged 18 years. His father Robert, who had gone from Tongue to see him, returned home with his son’s body for burial. His brother Charles Mackay was also killed in World War One serving in the Cameron Highlanders.