IRA informer Sean O'Callaghan claims that on 5 January 1976 , Twomey and Brian Keenan gave the go-ahead for the sectarian Kingsmill massacre , when 10 unarmed Ulster Protestant workmen were executed by the Provisional IRA in retaliation for a rash of loyalist killings of Catholics in the area . It was Keenan 's view , O'Callaghan claims , that " The only way to knock the nonsense out of the Prods is to be 10 times more savage "
Kingsmill massacre
Kingsmill massacre
Seamus Twomey