According to reports, during British rule in Ireland on the morning of the 21 November 1920, republicans under Michael Collins assassinated key figures in British administration, believed to be mi5. The network seemingly had links with Palestine and Cairo where they were previously stationed during the first world war. Collins was minister for finance and believed to be head of intelligence. Ten army officers died that day, mainly intelligence officers, though reportedly some associated police.
Later that day reportedly Dublin played Gaelic football against Tipperary at Croke Park in front of a crowd of 5000. Despite a reported unease, life carried on. According to reports a convoy of British soldiers drove into the stadium from the north west whilst the black and tans entered from the south. Shots were fired from the black and tans, and lasted about ninety seconds according to a witness. Resulted in the crowd running to the other side of the stadium. Reportedly the army fired fifty rounds of fire from machine guns. Among the dead was a young woman, two boys aged 10 and 11, and the football player Michael Hogan.
Reportedly the Dublin castle based British administration said the incident was unauthorised and the intention was to search all men on the way out of the stadium, but shots were fired only ten minutes into the game. Two military tribunals reportedly took place. One found shooting into the crowd unforgiveable, believed it to be unauthorised and blamed the police. No details of the other.