Stone is most notable for the "Milltown Massacre" in 1988, which took place at the predominantly Catholic Milltown Cemetery in Belfast during the funeral of three members of the Provisional Irish Republican Army, who had been shot by the British Army in Gibraltar. Stone later said he hatched the idea for Milltown after the IRA bomb killed eleven people attending a Remembrance Sunday service at the cenotaph in Enniskillen, County Fermanagh in 1987. Intent on killing top republicans, including Gerry Adams, Stone attacked the crowd with grenades and a pistol. He killed three people, including one member of the IRA, and injured sixty others. Stone was eventually overpowered by mourners, but was dragged to safety and arrested by members of the Royal Ulster Constabulary - he still walks with a slight limp as a result of the dislocated thigh bone he received in the aftermath of the attack. The attack was caught on television cameras, and provided some of the most savage images of the conflict.
Stone, who apparently objected to the newspapers' portrayal of him as a mad Rambo-style gunman, also confessed to shooting dead three other Catholics between 1984 and 1987. He claimed the victims were linked to the IRA, although it appears that they were unaligned civilians. At his trial he pleaded not guilty, but refused to offer any defence. Convicted of six murders, he was sentenced to life imprisonment with sentences totaling 684 years, with a recommendation he serve at least thirty years.
While behind bars Stone became the leader of the Ulster Freedom Fighters and was among many prisoners in HM Prison Maze to meet Mo Mowlam during the negotiations the government held with paramilitaries from both sides during peace negotiations in the mid-1990s, to get the loyalists to come to the negotiation table. He also collaborated with Martin Dillon on a book about his life entitled Stone Cold (ISBN 0-09-177410-1).
Stone had been living in East Belfast, London and Spain with his girlfriend Suzanne Cooper until the events of 24 November, 2006. In 2001 Stone and Ms Cooper exchanged bullet-proof jackets as Christmas gifts. He has nine children from two previous marriages, and three grand children.
Since leaving prison Stone had concentrated on work in the community and being an artist - a hobby he began in the Maze. His paintings are vivid and not so much political as topical. They fetch between a few hundred and a few thousand pounds each. Stone published his autobiography titled None Shall Divide Us, in which he claimed that he had received "specialist assistance" from RUC operatives in carrying out the cemetery killings. A second book and the auctioning of the jacket he wore at the Milltown Cemetery at a Scottish loyalist club for £10,000 have brought forward legislation to ban former convicted paramilitaries released through the Northern Ireland Peace Process from profiting from their crimes.
In March 2002, Stone and Cooper fled Ulster for France following death threats from loyalists opposed to the Peace Process. The terrorists' - believed to represent the Orange Volunteers - ultimate aim was the eventual destruction of the Good Friday Agreement and the end of Northern Ireland's troubled peace process. Following time in Birmingham, Stone returned to East Belfast.
Stone featured in the BBC2 television series Facing the Truth mediated by Archbishop Desmond Tutu where he met relatives of a victim of loyalist violence. Sylvia Hackett talked with Stone, who was convicted of murdering her husband Dermot, a Catholic delivery man. Although he previously admitted to the murder, Stone told his victim's widow that he had no direct responsibility, having been withdrawn after planning the attack. At the end of their meeting she forced herself to walk over to Stone and shake his hand - when he placed a second hand on hers, she recoiled and fled from the room.
In November 2006, he claimed that in the 1980s he had been "three days" away from killing the then leader of the Greater London Council and former Mayor of London, Ken Livingstone, over his invitations to Sinn Féin's Gerry Adams and Martin McGuinness to visit him in London. The plot was cancelled under fears that it had been infiltrated by Special Branch detectives.
The resumption of talks about power sharing and electing a First Minister between the parties at Stormont, which had only just resumed, had to be abandoned.
The then Secretary of State for Northern Ireland (Peter Hain) indicated that Stone's licence for release under the "Good Friday Agreement" would be revoked, and the full 638 year sentence for triple murder, terrorist charges and firearm charges be reimposed on him, in line with his sentencing in 1988.
Since his release in 1998, Stone has admitted to several other acts of terrorism, including murder. The Police Service of Northern Ireland (PSNI) are currently drawing a case for these to be put to the judge in due course. On 25 November 2006, Stone appeared in court in Belfast charged with attempting to murder Sinn Féin leaders Gerry Adams and Martin McGuinness. Stone faced a total of five charges of attempted murder following the incident at Stormont. He was also charged with possession of articles for terrorist purposes, possession of an imitation firearm, assault, grievous bodily harm, possession of an offensive weapon and possession of explosives. The court heard the articles allegedly for terrorist purposes included nailbombs, an axe and a garrotte. Michael Stone was remanded in custody until 22 December 2006. A letter written by Stone was published in the Belfast Telegraph on 29 November 2006. In the letter dated 24 November 2006, Stone described his "mission to Kill" Adams and McGuinness in detail, giving a description of his intended movements once inside the building.