Seán Heuston joined the Irish Volunteers soon after their formation in November 1913, eventually becoming a captain in Ned Daly’s 1st Battalion. He was assigned command at the Mendicity Institution on Easter Monday, to control the route between the Royal Barracks and the Four Courts for some hours, so that Commandant Ned Daly and the remainder of the 1st Battalion would have time to settle in at the Four Courts, In the event, Heuston and his force of less than 30 men held out for over two days. Surrounded and in a hopeless situation, Heuston surrendered on Wednesday to save the lives of his men.
Seán Heuston was tried by court-martial and sentenced to death. He was executed on 8 May, 1916. He was the youngest of those executed after the Easter Rising.
He was once described as a low-sized stocky figure with heavy dark eyebrows drawn down in a perpetual frown, ‘which gave him a somewhat forbidding appearance which was quickly dissipated when the rare smile lit up his face with a clear boyish gaiety’.