I'm not sure which agent you are recalling. The earliest I recall is when Vincenzo Vinciguerra confessed in 1984 to conducting a bombing in Peteano that had been previously blamed on the Red Brigade. He was Ordine Nuovo and the attack was performed with help from Italy's SID. He talked about an "entire mechanism" that was involved, what we now call Gladio. Prime Minister Andreotti openly admitted to Gladio's existence in 1990. The exact information about what happened and who funded it has never been fully documented. General Gerardo Serravalle publicly acknowledged at trial commanding it from 1971 to 1974. Bits and pieces got out over the years, but always very shadowy and slowly.
France's interior ministry and MOD have also acknowledged having a stay-behind force at times in the 20th century. Belgium eventually wrapped theirs into the SGR. Even the Nazi's had Werwolf (although it was 90% propaganda).
However, like the massacre at Brabant, we may never really know who did a certain thing and exactly why. Was it disillusioned Rijkswacht? Was it organized Rijkswacht? Was it related to roze balletten?
At the end of the day, I'm not sure that it matters what banner flies above a group of people that will engage in despicable acts in the name of justice, glory, or money. Whether it is done ostensibly in the name of 'Murica or Christ or family or a newfound savior, you're an outlier at best.