Peter Joseph Cleary ( 18 September 1950 – 15 April 1976 ) was an Irish republican and a leading member of the 1st Battalion of the Provisional Irish Republican Army ( IRA ) 's South Armagh Brigade . He held the rank of Staff Officer and served as the unit 's treasurer . He was implicated by journalist and author Joe Tiernan in the killing of Ulster Defence Regiment ( UDR ) corporal and alleged Ulster Volunteer Force ( UVF ) member Robert McConnell . Ten days after McConnell 's killing , Cleary was shot dead by the Special Air Service ( SAS ) after being arrested at the home of his girlfriend outside Forkhill . He was widely believed to have been the mastermind behind the Kingsmill massacre , when ten Ulster Protestant workers were taken from their work van and shot dead by the roadside . He was the first person in Northern Ireland to be killed by the SAS , following the admission of their deployment there in January 1976 . According to the SAS , he was shot after attempting to take the rifle from the officer who was guarding him in a bid to escape
Kingsmill massacre
Kingsmill massacre
Peter Cleary