Those responsible for the attack belonged to the Glenanne gang, a secret alliance of loyalist militants, Royal Ulster Constabulary (RUC) police officers and UDR soldiers.

[5] UK Home Secretary Roy Jenkins introduced the Prevention of Terrorism Act, which gave the government unprecedented powers against the liberty of individuals in the United Kingdom in peacetime.

[6] The existence of these talks led unionists to believe that they were about to be abandoned by the British government and forced into a united Ireland; as a result, the loyalist paramilitary groups reacted with a violence that, combined with the tit-for-tat retaliations from the IRA (despite their ceasefire), made 1975 one of the "bloodiest years of the conflict".

[12] Journalist Joe Tiernan suggested that Hanna was shot for refusing to participate in the Miami Showband attack and that he had become an informer for the Gardaí in exchange for immunity from prosecution for the Dublin bombings.

[14] Jackson was an alleged RUC Special Branch agent who was said by Yorkshire Television's The Hidden Hand: The Forgotten Massacre programme to have had links to both the Intelligence Corps and Captain Robert Nairac.

O'Toole was noted for his good looks and popularity with female fans,[20] and was described by the Miami Showband's former bass guitarist, Paul Ashford, as having been the "greatest soul singer" in Ireland.

At about 2:30 am, when the band was seven miles (11 km) north of Newry on the main A1 road, their Volkswagen minibus (driven by trumpeter Brian McCoy with bassist Stephen Travers in the front seat beside him) reached the townland of Buskhill.

[21][22][31] Travers thought that McCoy, a Protestant from Northern Ireland, was familiar with security checkpoints and had reckoned the regular British Army would be more efficient than the Ulster Defense Regiment (UDR), who had a reputation for unprofessional and unpredictable behaviour, especially toward people from the Republic.

[21][36] He suggested that had all gone according to plan, the loyalist extremists would have been able to clandestinely bomb the Republic of Ireland, yet claim that the band were republican bomb-smugglers carrying explosives on behalf of the IRA.

[20] Following the explosion pandemonium broke out among the remaining gunmen; shouting obscenities, they started shooting the dazed band members, who had all been blown down into the field below the level of the road from the force of the blast.

They also discovered a stolen white Ford Escort registration number 4933 LZ,[43] which had been left behind by the gunmen, along with two guns, ammunition, green UDR berets and a pair of glasses later traced to James McDowell, the gunman who had allegedly ordered the shootings.

[34] Afterward, as Travers recovered in hospital, the other survivor Des McAlea gave the police a description of McDowell as the gunman with a moustache and wearing dark glasses who appeared to have been the leader of the patrol.

[50] The stolen Ford Escort belonged to a man from Portadown, who according to Captain Fred Holroyd, had links with one of the UVF bombers and David Alexander Mulholland, the driver of the bomb car which had been left to explode in Parnell Street, Dublin, on 17 May 1974.

[51] An independent panel of inquiry commissioned by the Pat Finucane Centre has established that among the weapons actually used in the killings were two Sterling submachine guns and a 9 mm Luger pistol serial no.

It was released under the heading Ulster Central Intelligence Agency – Miami Showband Incident Report:[20][48][42] A UVF patrol led by Major Boyle was suspicious of two vehicles, a minibus and a car parked near the border.

[19] The Irish Times reported that on the night following the attack, the British ambassador Sir Arthur Galsworthy was summoned to hear the Government of Ireland's strong feelings regarding the murder of the three band members.

[22] According to Peter Taylor, the Provisional IRA's gun and bomb attack on the loyalist Bayardo Bar in Belfast's Shankill Road on 13 August was in retaliation for the Miami Showband ambush.

[59] Two days later, Portadown disc jockey Norman "Mooch" Kerr, aged 28,[60] was shot dead by the IRA as he packed up his equipment after a show at the Camrick Bar in Armagh.

The IRA said it killed him because of an alleged association with British Army officer and member of 14th Intelligence Company, Captain Robert Nairac, and claimed it was in possession of his diary, which had been stolen in Portadown.

Former serving Secret Intelligence Service agent Captain Fred Holroyd, and others, suggested that Nairac had organised the attack in co-operation with Robin Jackson and the Mid-Ulster UVF.

[72][73] Surviving band members Stephen Travers and Des McAlea told police and later testified in court that a "man in a different uniform and beret" with a "crisp, clipped English accent" oversaw the attack, the implication being that this was Nairac.

I was told by a source close to "Mr. A" and another loyalist hitman that Nairac was not present at either murder [Miami Showband and John Francis Green].Travers had described the English-accented man as having been of normal height and thought he had fair hair, but was not certain.

[44] The independent panel of inquiry commissioned by the Pat Finucane Centre concluded that there was "credible evidence that the principal perpetrator [of the Miami Showband attack] was a man who was not prosecuted – alleged RUC Special Branch agent Robin Jackson".

[35] Dillon also opined in God and the Gun: The Church and Irish Terrorism that the dead bombers, Harris Boyle and Wesley Somerville, had actually led the UVF gang at Buskhill.

Griffin suggests that McCoy, who originally came from Caledon, County Tyrone, and had strong UDR and Orange Order family connections, was possibly approached at some stage by Jackson with a view of securing his help in carrying out UVF attacks in the Irish Republic.

Their name comes from a farm in Glenanne, County Armagh, which was owned by RUC reservist James Mitchell; according to ex-RUC Special Patrol Group officer John Weir, it was used as a UVF arms dump and bomb-making site.

The 55-cent stamp, designed with a 1967 publicity photograph of the band, included two of the slain members, Fran O'Toole and Brian McCoy, as part of the line-up when Dickie Rock was the frontman.

The Historical Enquiries Team (HET), which was set up to investigate the more controversial Troubles-related deaths, released its report on the Miami Showband killings to the victims' families in December 2011.

[69] Stephen Travers decried: "We believe the only conclusion possible arising from the HET report is that one of the most prolific loyalist murderers of the conflict was an RUC Special Branch agent and was involved in the Miami Showband attack".

[101] A Netflix documentary titled ReMastered: The Miami Showband Massacre was released on 22 March 2019, highlighting the efforts of Stephen Travers to track down who authorized the attack, for what purposes, and to get an admission of culpability.