Just after three o'clock on Sunday, November 21, 1920, groups of RIC policemen, Auxiliaries and members of the notorious 'Black and Tans' arrived at a Gaelic football match at Croke Park in Dublin and began firing at spectators and players. Within 90 seconds, 14 men, women and children lay dead or dying.
The killings were roundly condemned by the British military and civil authorities, but the hurt that was caused that day helped shape the GAA, and it took almost 90 years more before players of other sports were permitted to play on what some in the association saw as holy ground.
The attack on Croke Park did not come out of the blue but was a reprisal for the killing of 16 men earlier that day. The Anglo-Irish War, or War of Independence, was under way, and IRA leader Michael Collins organised a series of attacks on British intelligence officers in various homes around the city. The dawn raids claimed 16 lives - 10 Army officers, one RIC sergeant, two cadets in the RIC Auxiliary Division and three civilians.
Among those shot dead at Croke Park was Michael Hogan, a half-back on the Tipperary team - his name is now given to the main stand in the stadium and he is revered in GAA mythology. But Hogan was not the only sporting victim of the day.
One of those who died of his wounds some weeks later was Hugh Ferguson Montgomery, whose family came from Donegal and one of whose cousins was the famous Field-Marshall Bernard Law Montgomery of El Alamein.
Montgomery was born in 1880 in India, where his father was a clergyman, and, after school at Marlborough College, Hugh joined the Royal Marines.
His postings were mostly in southern England, meaning he was able to pursue his sporting interests as a cricketer. His career was undistinguished - just one 50 in 17 first-class games, but it lasted from 1901 to 1912.
Montgomery mostly played for Somerset, for whom he scored his best score of 50 against Sussex in May 1904, but also played first-class matches for MCC, Royal Navy.
He played plenty of good cricket at a lower level, with his finest hour coming for MCC against Monmouthshire at Rodney Parade in 1905. His side included Test players Len Braund, Walter Mead and Sammy Woods, but Montgomery was the only century maker, falling for 107.
By then he had married Ethel Cramer and attained the rank of Captain, winning promotion to the Naval War Staff Operations branch in 1913. He was a Major by 1915 when he arrived in France. There he won six military decorations, including the DSO and CMG, as well as the French Legion d'Honneur Croix de Guerre.
At war's end he served with the Army of the Rhine before on February 12, 1920 he was posted to Dublin, where he was among the top 10 ranked officers in the HQ staff of Irish Command.
The attacks of Bloody Sunday began shortly after daybreak on November 21. The residence of Mrs Gray on Pembroke Street - between Baggot Street and Leeson Street - was divided into flats and several officers lived there.
One IRA account of the attacks read: "The operation began at 9:00am, when members of the Squad entered 28 Pembroke Street. The first British agents to die were Major Dowling and Captain Leonard Price. Andy Cooney of the Dublin Brigade removed documents from their rooms, before three more members of the Gang were shot in the same house: Captain Keenlyside, Colonel Woodcock, and Colonel Montgomery."
Montgomery was unlucky - he wasn't on the original list of targets of Collins' assassins. Hearing the gunshots, he came out of his room and was shot.
A news report read: "The residence of Mrs Gray was raided at nine o'clock this morning by about 20 men, some of whom came on bicycles. Colonel Woodcock was fired at as he came downstairs. He appeared to have taken unawares by the raiders who were in the hall. He called out to Colonel Montgomery who was coming out of his room and was wounded in the body."
A conflicting account was given by one of Collins' squad, Larry Nugent, who testified that Montgomery was in charge of intelligence gathering.
His version of his shooting is also very different: "When the men who executed Montgomery in Pembroke St. entered his room and told him who they were, he asked that his wife be allowed to leave the room. This request was granted. He then stood to attention and said 'I know your mission, boys, do your duty'."
Montgomery died three weeks later on December 10. His body was carried to the docks with a full procession and he was buried at Brompton Cemetery in London. His widow was awarded £8,000 compensation and died in 1970, aged 90.
The house where Montgomery and his two colleagues were shot is now an office building and, in a sporting twist, one of the firms now based there is the solicitors practice of Tony Hanahoe, twice All-Ireland winning captain of Dublin in the 1970s.