 Breen and Buchanan were returning from an informal cross-border security conference in Dundalk with senior Garda officers when Buchanan's car – a red Vauxhall Cavalier — was flagged down and fired upon by six IRA gunmen, who the policemen had taken for British soldiers.Buchanan was killed outright whilst Breen, suffering gunshot wounds, was deliberately shot in the back of the head after he had left the car waving a white handkerchief.They were the highest-ranking RUC officers to be killed during the Troubles.