On this day in 1972, 26 unarmed demonstrators and bystanders were shot by members of the British Army in Derry, Northern Ireland, on what came to be known as Bloody Sunday.

13 of those shot – all men, seven of them teenagers – died of their wounds on the day, while another wounded man died four months later. Two demonstrators were also run down by army vehicles.

As the video above shows, the incident occurred during a march protesting against the then British policy of internment of terrorism suspects without trial, and against the banning of marches and parades by the Northern Irish government in an attempt to quell violence.

The march against internment

Using barricades, the Army had prevented the marchers from reaching the city’s Guildhall Square, redirecting them towards Free Derry Corner. Reaching the barricades, a large group of demonstrators – mainly young men – broke off from the march and began hurling stones and bottles at the soldiers.

Such confrontations were a regular occurrence, and witnesses say the rioting was not intense; but at around this point, soldiers shot and wounded two men, as they were fired on by an IRA sniper. Who shot first has never been conclusively established.

Members of the 1st Brigade, The Parachute Regiment (1 Para) were ordered into the Bogside and the use of live rounds was authorised. As they moved forward, shots were fired indiscriminately into the fleeing crowd.

A member of the Parachute Regiment clashing with a rioter on Bloody Sunday

The Widgery Tribunal, which was convened and reported very quickly after the event, largely exonerated the soldiers. In 1998 a new inquiry headed by Lord Saville concluded that all of those shot on the day were unarmed, and that the killings were both "unjustified and unjustifiable".

[Read more: November 15, 1985 - Anglo-Irish Agreement sparks angry response from loyalists]

[Read more: July 28, 2005 - IRA declares end to war against Britain]