Educated by the Christian Brothers, he later worked as a railway clerk in Limerick and while there took an active part in Fianna Éireann, of which he was an officer.

[6] He was Director of Training for Fianna Eireann as well as being Vice-commandant of the Dublin Battalion and Commander of the 5th company from August 1915 to Easter 1916.

[8] Acting under orders from James Connolly, Heuston was to hold this position for three or four hours, to delay the advance of British troops.

The dispatch was carried by two Volunteers, P. J. Stephenson and Seán McLaughlin, who had to avoid both sniper fire and British troops across the city.

Not everyone approved but the order was obeyed and we destroyed as much equipment as we could before giving ourselves up...[2] According to the statement given by Séamus Brennan to Piaras F. Mac Lochlainn, author of Last Words, the British troops were "infuriated when they saw the pygmy force that had given them such a stiff battle and caused them so many casualties".

An officer asked who was in charge and Sean stepped out in front without a word… We were forced to march to the Royal (now Collins) Barracks with our hands up, held behind our heads.

I had a small cross in my hand, and though blindfolded, Seán bent his head and kissed the Crucifix; this was the last thing his lips touched in life.

He was perfectly calm, and said with me for the last time: ‘My Jesus, mercy.’ I scarcely had moved away a few yards when a volley went off, and this noble soldier of Irish Freedom fell dead.

[2][6]Father Albert concluded: Never did I realise that men could fight so bravely, and die so beautifully, and so fearlessly as did the Heroes of Easter Week.

On the morning of Sean Heuston's death I would have given the world to have been in his place, he died in such a noble and sacred cause, and went forth to meet his Divine Saviour with such grand Christian sentiments of trust, confidence and love.