He was arrested and questioned over various crimes, including the murder of a Royal Ulster Constabulary police officer and a British Army soldier, but was eventually convicted and sentenced only for firearms offences in 1973.
O'Hagan also worked with the Channel 4 programme Dispatches on alleged collusion in multiple sectarian murders by security forces and Loyalists (see Glenanne gang).
Criminal prosecution of five LVF members was attempted in the late 2000s and early 2010s, but the case for the Crown collapsed after one defendant, who had turned supergrass, was ruled to be an unreliable witness.
[7] As a teenager, O'Hagan joined the Official Sinn Féin (later the Workers' Party), and made friends with then-general secretary Máirín de Burca,[4] with whom he pelted Richard Nixon's car with eggs during a 1970 visit to Dublin.
[7] Back home from Dublin, O'Hagan had joined the Lurgan unit of the Official IRA, enjoying their socialist-republican policies and military wing.
[5][1] On 15 December 1972, Police Constable George Chambers and his colleagues were driving through Lurgan's Kilwilkie estate after delivering Christmas presents to the house of an injured child.
Later that year, he was arrested after a shooting in a Lurgan bar, where a Protestant man named William Houston was shot in the leg by O'Hagan's group.
[1] While his journalism career began in the late 1970s, he was involved with local paramilitary activities until the early 1980s, being a suspect in the armed robberies of a Lurgan post office and a shop.
The paper reported on the sectarian violence of the Troubles, with a specific focus on the crimes of Robin Jackson (known as "The Jackal"), an Ulster Volunteer Force (UVF) leader who had been involved in various brutal killings.
In 1999, he campaigned for Ed Moloney regarding the handing over of vital information, and gave evidence on behalf of Sean McPhilemy in his libel case against the Sunday Times.
[13][5] While in their possession, he underwent an interrogation with the IRA's Internal Security Unit (known as the "Nutting Squad"), and allegedly spent two nights with a hood placed over his head.
[5] In the final years of his life, O'Hagan continued reporting on paramilitaries and crime, publishing stories about the actions of neo-Nazi group Combat 18 regarding Lurgan solicitor Rosemary Nelson and the supposed ethnic cleansing of Portadown.
[12] O'Hagan's reporting was often supported by insider information, such as former loyalist activist Barrie Bradbury, whose life was threatened several times by paramilitary groups.
[12] On 28 September 2001, O'Hagan and his wife Marie went for their weekly drink at The Central Bar, popularly known as Fa' Joe's pub,[17] on Lurgan's Market Street, arriving there at around 8pm.
At 10:30pm, while walking down Westfield Gardens and near the Mourneview estate, a silver Subaru Impreza parked outside a neighbour's house began to slowly move forwards.
[19] The gun used to kill him had supposedly been used before in a feud murder, brought to Lurgan from Dungannon in County Tyrone,[19] with Susan McKay suggesting the killer was a member of Billy Wright's original Ratpack.
[5] On 29 September 2001, John Reid, then-Secretary of State for Northern Ireland, denounced O'Hagan's death as a "barbaric killing" and vowed to track down his murderers.
Martin McGuinness, then-Education Minister for Sinn Féin, called Reid "very foolish" for walking back on actions to declare the ceasefire broken, following O'Hagan's murder.
[25] Bertie Ahern, the then-Taoiseach, called it "senseless and brutal", while Sir Reg Empey, the Acting First Minister of Northern Ireland, denounced O'Hagan's murder as "an attack on democracy itself".
[26] Upper Bann MLA and leader of the Ulster Unionist Party David Trimble stated that "[he was] shocked and appalled by this cowardly act, which must be condemned by all right-thinking people" and called on the British government to seriously consider whether the LVF ceasefires must be regarded as violated.
[26][19] The general secretary of the National Union of Journalists, John Foster, also questioned whether the killing had caused the ceasefire between paramilitary groups to be broken, saying "one of our members has died and that's one too many".
[19] Soon after O'Hagan's assassination, new graffiti appeared on the Mourneview estate with the words "Shove ur dove, and Marty", and members of the Orange Volunteers website welcomed his death as "making the news instead of writing it".
Sinn Féin MLA for Upper Bann Dara O'Hagan said the attack was part of an ongoing attempt by loyalist bitter enders to provoke Irish republican paramilitaries back into armed conflict.
[29] A similar event happened in Lurgan five years earlier, when Billy Wright's men murdered a Catholic taxi driver as a "birthday present" for their leader.
[35] Hyde had confessed to a number of offences in September 2008 as a member of the LVF involving drugs, arson, firearms, and withholding information regarding a murder.
[38] While Hyde originally agreed to testify against O'Hagan's killers, a decision was made by Director of Public Prosecutions Barra McGrory in January 2013 to dismiss the use of his witness statement as unreliable.
[44] On the 19th anniversary of his death, the NUJ released a statement calling for UK and Ireland leaders Boris Johnson and Micheál Martin to support an independent inquiry, and said the failure to convict O'Hagan's killers "emboldens those who see themselves as being above the law".
[45] In September 2014, OSCE Representative on Freedom of the Media Dunja Mijatović called for UK authorities to launch an investigation into the murder, arguing that "the failure to prosecute can create an environment of impunity for those who might attack journalists".
[21] Several of O'Hagan's former colleagues at the Sunday World have alleged police involvement in covering up his death: On 28 May 2015, BBC aired a Panorama documentary entitled Britain's Secret Terror Deals, which investigated claims that British security forces colluded with paramilitary groups.
[54] Since O'Hagan's death, Sunday World owner Independent News & Media has afforded security measures to its journalists, such as installing bulletproof windows and panic buttons in their houses.