In the early 90 's , he was appointed as head of the " Tango Squad " , a group of Gardai who spent the large majority of their on-duty time monitoring the activities of Martin Cahill , a notorious Irish mob boss . The Tango Squad proved to be successful in thwarting many of Cahill 's activities and preventing him from taking on any major criminal objectives ; this helped boost Callinan 's career significantly . By the time of Cahill 's assassination by the Provisional IRA in 1994 , Callinan was a detective inspector . Investigations into the Omagh bombing , and its perpetrators , the Real IRA , were led by Callinan . He also took part in Garda reviews of the Ryan Report and the Murphy Report
Omagh bombing
Omagh bombing
Martin Callinan