I think the Dominic Behan version starts "Give me a Parabellum and a couple of hundred shells; take me to the Murder Gang and we'll blow them all to hell".

(The Murder Gang were the British assassins who were themselves assassinated by Michael Collins's Squad, aka The Twelve Apostles.)

Incidentally, the meeting in the Republican Outfitters was not actually to talk about Breen, but had been arranged before the Church Avenue ambush in the house of Prof Carolan which wounded both Treacy and Breen - it was a meeting to set up the Flying Columns in Tipperary.

As stated by Big Tim, Clancy and McKee were murdered after Treacy's killing by the same Murder Gang.