In Canada he lived at 89 Peter Street Toronto with his brother John. He was employed as a warehouse man. He enlisted in the Canadian Army on the 17 January 1916 joining the 15 Battalion (48 Highlanders) Canadian Infantry.
Once he had completed his military training he was sent to France and he fought on the Western Front with the Canadian Forces.
Private Eric Mackay was killed in action on the 21 of April 1917 during the Battle of Arras, the first phase of the battle was over by this time and the Canadian Forces were preparing to push forward on the village of La Coulotte. The British and Canadian Armies suffered terrible losses at Arras, as they tried to push through the enemy Hindenburg line and win the war.