The testimony comes from Tom Barry himself
In a 1964 interview he said that he told his men that the Auxiliaries would take no prisoners. This would imply that his men would give no quarter.
Barry said it was a brutal fight and a savage fight. This hints at him slaying prisoners.
He said that the combat became hand to hand. This again suggests killing with weapons other than guns and at very close quarters.
The Crown forces said that the corpses were mutilated with axes. Is Barry tacitly admitting this?
”we were now hard cold and ruthless as our enemy. They had gone down in the mire to destroy our nation and down after them we had to go.” So wrote Barry. He thought his foes foul but states that he was no better.