McCann saw himself as a Marxist revolutionary
Joe McCann was an Official IRA commander who believed in creating a socialist Ireland.
He took part in Northern Ireland's first march for equal rights for Catholics in 1968 and supported an "Army of the people" involved in social struggle, his family have said.
At the start of the Troubles in 1969 the IRA had split into Official and Provisional organisations. Both opposed partition and refused to recognise the Governments of either the Republic of Ireland or Northern Ireland.
While the northern-dominated Provisionals advocated violence, the Officials, with a leadership based in the Republic, pursued a policy of creating a socialist Ireland through largely peaceful means.
It feuded with the Provisionals and targeted members of the security forces, but research has linked it to fewer than 50 killings between 1969 and 1979.
The Provisionals killed around 1,700.
McCann was involved in the Belfast Housing Action Committee, seeking better housing and establishing co-operatives, his family said.
He reportedly took part in fighting during a curfew on the Falls Road in west Belfast in July 1970.
And in August 1971 in the Markets area of the city centre clashed with British troops as commander of the Official IRA.
He was killed on April 15, 1972 in Joy Street in The Markets. Ten cartridge cases were found close to his body, indicating that he had been shot repeatedly. Bullet holes were also visible in the walls of houses.