Guns linked to the murders of 10 Protestant workmen at Kingsmill were used in over 40 other terrorist attacks.
The weapons used to kill the Kingsmill workers have a bloody trail and a fuller picture of that emerged at an ongoing inquest into the murders on Tuesday.
Families of those shot dead that night 41 years ago heard that 11 guns linked to the attack were used in up to 45 other serious terrorist incidents over a 15-year period.
A police intelligence officer - known as J2 - was questioned about that weaponry.
The inquest - which resumed on Monday after a lapse of almost a year - heard that a small group of terrorists in south Armagh may have been using the weapons and that between 1974 and 1976 they were linked to 10 other murders and several attempted murders.
The witness - speaking from behind a screen - agreed that was a fair assessment.
Among the weaponry in focus - is a gun linked to the murders of RUC Chief Superintendent Harry Breen and Superintendent Bob Buchanan in 1989.
The senior policemen were shot dead in an ambush in south Armagh.
There were other guns detailed at the inquest - including riles and shotguns.
Then J2 was asked about links between the weapons and the Provisional IRA - who have always denied involvement in the Kingsmill killings.
J2 told the inquest that it was the current PSNI's assessment that the Provisional IRA were behind the attack - using the South Armagh Republican Action Force as cover.
The only survivor of the attack, Alan Black, said outside the court: “When you hear it read out in a deadpan voice, something that you always thought of with emotion, when you hear it read out in court it’s an eerie feeling.
“There’s people in that court, the coroner, the families’ legal teams are doing everything in their power to get this inquest forward but there is a hidden hand that is trying to frustrate this inquest.”
The inquest was adjourned early in the afternoon and will resume on Wednesday.