Soldiers of the British Army's Parachute Regiment opened fire on a crowd of civil rights demonstrators marching through the Bogside district of Derry, killing 13 people outright (a 14th died later of his wounds) and wounding many more. None of those shot was found to be armed. The killings radicalized nationalist opinion, swelled recruitment for the Provisional IRA, and became one of the defining atrocities of the Troubles.
Around 15,000 people had gathered for a march organized by the Northern Ireland Civil Rights Association, protesting the policy of internment without trial. British authorities had banned the march, and paratroopers were deployed to contain it. As some marchers threw stones, soldiers moved into the Bogside and, in the space of about ten minutes, fired more than 100 rounds into the crowd.
Victims included teenagers and a man shot while crawling away from soldiers; several were shot in the back. The British Army initially claimed soldiers had been fired upon first and that many victims were IRA members or had been carrying weapons—claims later proven false by the exhaustive Saville Inquiry, which took 12 years and reported in 2010 that the killings were unjustified and unjustifiable.
The day, forever after known as Bloody Sunday, became a rallying cry for Irish nationalism worldwide—U2's 1983 song 'Sunday Bloody Sunday' carried its memory to a global audience. Prime Minister David Cameron formally apologized in the House of Commons in 2010, calling the killings 'unjustified and unjustifiable,' but for many families in Derry, that apology came nearly four decades too late.