Arriving home, he learned that the Rising was about to begin in Dublin on the next day,
Easter Monday, 24 April 1916. Despite his efforts to prevent such action (which he felt could only lead to defeat), he set out to
Liberty Hall to join Pearse,
James Connolly,
Thomas MacDonagh,
Tom Clarke,
Joseph Plunkett,
Countess Markievicz,
Seán Mac Diarmada,
Éamonn Ceannt and their Irish Volunteers and
Irish Citizen Army troops. Arriving in his
De Dion-Bouton motorcar, he gave one of the most quoted lines of the rising – "Well, I've helped to wind up the clock -- I might as well hear it strike!" Another famous, if less quoted line, was his comment to Markievicz, "It is madness, but it is glorious madness." His car was used to fetch supplies during the siege, and later as part of a barricade on Prince's Street, where it was burned out. He fought with the
GPO garrison during Easter Week. One of the first British prisoners taken in the GPO was Second Lieutenant AD Chalmers, who was bound with telephone wire and lodged in a telephone box by the young Volunteer Captain and IRB activist
Michael Collins. Chalmers later recalled O'Rahilly's kindness to him. In a statement to a newspaper reporter, he said that he was taken from the phone box after three hours and brought up to O'Rahilly, who ordered: "I want this officer to watch the safe to see that nothing is touched. You will see that no harm comes to him". On Friday 28 April, with the GPO on fire, O'Rahilly volunteered to lead a party of men along a route to
Williams and Woods, a factory on Great Britain Street (now
Parnell Street). A British machine-gun at the intersection of Great Britain and Moore streets cut him and several of the others down. O'Rahilly slumped into a doorway on Moore Street, wounded and bleeding badly but, hearing the British marking his position, made a dash across the road to find shelter in Sackville Lane (now O'Rahilly Parade). He was wounded diagonally from shoulder to hip by sustained fire from the machine-gunner. He bled to death slowly in a doorway in Moore Lane (latterly O'Rahilly Place) overnight alone. He managed to scribble off a farewell note to his wife and that night was heard crying for water. According to ambulance driver Albert Mitchell (in a witness statement more than 30 years later), O'Rahilly still clung to life 19 hours after being severely wounded, long after the surrender had taken place on Saturday afternoon. The following is an extract:
Desmond Ryan's
The Rising maintains that it "was 2.30pm when Miss O'Farrell reached Moore Street, and as she passed Sackville Lane again, she saw O'Rahilly's corpse lying a few yards up the laneway, his feet against a stone stairway in front of a house, his head towards the street". ==Memorial==