County Tyrone, with sustained automatic-rifle fire, anti-tank rockets, and rounds fired from an improvised mortar which was operated by O'Callaghan. During this attack a female UDR recruit was killed. On 23 August 1974 O'Callaghan killed Detective Inspector Peter Augustine Flanagan, a 47-year-old Catholic police officer and head of the Omagh Division of the Royal Ulster Constabulary's Special Branch, by shooting him repeatedly with a handgun in a two-man IRA attack in a public house in the town of Omagh in County Tyrone. Irish Government agent within the IRA In 1976, aged 22, O'Callaghan ended his involvement with the IRA after becoming disillusioned with its activities. He later recalled that his disenchantment with the IRA began when one of his compatriots openly hoped that a female police officer who had been blown up by an IRA bomb had been pregnant so they could get "two for the price of one." He was also concerned with what he perceived was an undercurrent of ethnic hatred in its rank and file towards the Ulster Scots population. He left Ireland and moved to London. In May 1978, he married a Scottish woman of Protestant unionist descent. During the late 1970s, he ran a successful mobile cleaning business. However, he was unable to fully settle in his new life, later recalling: "In truth there seemed to be no escaping from Ireland. At the strangest of times I would find myself reliving the events of my years in the IRA. As the years went on, I came to believe that the Provisional IRA was the greatest enemy of democracy and decency in Ireland". In 1979 O'Callaghan was approached by the IRA seeking to recruit him again for its paramilitary campaign. In response, he decided to turncoat against the organisation and become an agent within its ranks for the Irish Government. In his memoir, O'Callaghan described his reasoning as follows: I had been brought up to believe that you had to take responsibility for your own actions. If you did something wrong then you made amends. I came to believe that individuals taking responsibility for their own actions is the basis for civilisation, without that safety net we have nothing. O'Callaghan later told authors Kevin Cullen and Shelley Murphey that he decided to become a double agent even though he knew that even those who hated the IRA as much as he now did have a low