Promoted through ranks.
2nd Canadian Divisional Signal Coy - War Diary Entry:
1915-12-29 - Page 15 - No 184 Pte. Lockhart W. E. (CAMC) struck off strength 17-12-15
From the “University of Toronto / Roll of Service 1914-1918”, published 1921
WILLIAM ERIC LOCKHART Mar. 8, 1893 – June 12, 1917
Lieutenant, Canadian Engineers, Signals, and Royal Flying Corps. Son of the late W. T. Lockhard, M.P.P.; b. Newcastle; ed. Newcastle P.S. and H.S.,Bowmanville H.S.; Applied Science 1911-15, B.A.SC. (Civ. Eng.); Psi Delta Psi.
In November 1914 he enlisted in the 2nd Divisional Signal Company of the Canadian Engineer, In which he was later promoted Sergeant, and went overseas in May 1915. He went to France with this unit in September, and served at the front, mostly in the Ypres area, till December when he was invalided with pleurisy and remained in England for several months. In February1917 he received his commission in the Engineers, and shortly afterwards was seconded to the R.Flying Corps. He returned to France on June 2nd, being appointed to the 100th Squadron, and beganNight flying over the lines. Ten days later, when he was acting as machine-gunner, the plane fellJust before crossing the enemy’s lines, killing him instantly. Buried at Aire new St. Omer.
Details of death from Ancestry.com which includes a digitized image of the casualty form from the "Canada, War Graves Registers (Circumstances of Casualty), 1914-1948" database. Note this only states he was Killed in Action with no other details.