According to Royal Ulster Constabulary (RUC) Special Patrol Group (RUC) officer John Weir, Hanna was a leader of one of the two UVF units that planned and carried out the Dublin car bombings on 17 May 1974, which killed 26 people. Former British soldier and psychological warfare operative Colin Wallace suggested that Hanna had been the principal organiser of the Dublin attacks. Journalist Joe Tiernan confirmed this and stated that he had also directed the Monaghan bombing which occurred that same evening and claimed an additional seven lives.