It took more than a month before the first gun murder of the year but the slaying of drug dealer Alan McNally (36) at the packed Cappagh Nua pub in Finglas on February 2 was a sign of things to come.
Detectives investigating McNally's cold-blooded shooting believe the chief suspect also killed his brother Graham in February, 2009.
There have been no charges in the case even though gardai have arrested the chief suspect along with a gangster who wore a white Scream mask and kept lookout during the murder, as well as a sister and niece of the man who ordered the hit.
Sources say that McNally (right) was targeted because he publicly boasted about getting revenge for the death of his brother, who was shot dead by slain crimelord Eamon 'The Don' Dunne's gang in January 2009.
Less than a week after McNally was murdered, the country was shocked by the shooting dead of 16-year-old Melanie McCarthy McNamara as she sat in the back of a car in Tallaght on February 7. Two young men have been charged with her murder.
Just two days later, suspected drug dealer Andrew Allen (24) from Derry was blasted to death by vigilantes in Buncrana, Co Donegal. Mr Allen's 34-year-old girlfriend escaped the attack at their home uninjured.
No one has been charged in connection with the death but dissident group Republican Action Against Drugs claimed responsibility for the murder.
In April, a man aged in his 50s and from Northern Ireland as well as a man in his 30s was arrested in connection with Mr Allen's murder but were later released without charge.
On March 6, in a double murder atrocity, gangland hardman Andy Barry was shot dead at a house he was renting in Kilcock, Co Kildare, along with his pal, Lithuanian national Zilvinas Varnauskas, also aged 31. Two other men were also injured in the reckless gun attack.
Detectives initially worked on the theory that Barry and his mate were targeted by a Tallaght drug dealing gang who Barry (right) was feuding with but now believe the psychotic bully may have been shot dead by his own gang.
Two men have been arrested for withholding information in the case but there has been no charges.
As gangland crime threatened to spiral out of control, gardai were forced to deal with their second double murder in just 24 hours when Anthony Burnett (32) of Croke Villas, and 25-year-old Joseph Redmond (below), Ballybough House, both in north inner city Dublin, were found shot dead in a stolen car at Ravensdale near, Dundalk, Co Louth.
Gardai believe the unfortunate duo were the victims of a gang of criminals from the Coolock area who are led by so-called gang boss 'Mr Big'.
Among the suspects are two notorious brothers who have been nicknamed 'The Taliban' and are also the chief suspects for the double murder of two men in Finglas in November 2010.
One of the brothers is currently locked up, facing charges in relation to an attack on a former associate, while another has fled the country.
There have been no arrests in the double murder case.
After four shocking gangland murders in just 24 hours, it would be September 2 before the next gun murder happened in Ireland.
On that night, Limerick criminal Robert Sheehan (21) was shot dead as he attended a wedding at Bunratty Castle in Co Clare.
There have been no charges in the case but six men have been arrested and questioned about it.
Sheehan was jailed for his part in a petrol bomb attack on a car in Moyross on September 10, 2006, which left Gavin Murray, then aged 4, and his sister, Millie, then aged 6, with horrific burns.
Mr Sheehan, then aged 16, acted as lookout for two others who were also jailed for their part in the attack, which shocked the nation.
Just weeks before his murder, he was involved in an incident in which another man was stabbed in Moyross.
The following day in what was the highest-profile gun murder of the year, Real IRA terror chief Alan Ryan (32) was shot dead as he walked with friends in Clongriffin, north Dublin.
His murder was organised when a number of the most dangerous gangs in the capital clubbed together after Ryan extorted money from them and engaged in a campaign of violent harassment.
He was killed close to his home when two gunmen opened fire on him and one of his associates.
A car carrying what gardai believe were two gunmen pulled up and at least one passenger got out and started firing at Ryan and his friend Aaron Nealis, who was shot in the leg.
Two men have been charged with withholding information in the case and there have been three arrests.
On September 24 two men Gerard Eglington (27, below) and 32-year-old Declan O'Reilly, were gunned down in front of their children in separate attacks.
Eglington, below, who was a mortal enemy of the 'Fat' Freddie Thompson gang faction, was blasted to death in his home in Portarlington, Co Laois.
There have been no arrests in the case.
Just under 12 hours later in an unrelated attack, O'Reilly, who was not involved in organised crime, was shot after a lone gunman jumped from a stolen silver BMW 3 Series. The victim was blasted as he walked along the South Circular Road with his 11-year-old son.
The assassin shot O'Reilly in the chest and neck before jumping back inside the vehicle which fled eastwards. The car was found burnt out 1.5km away at O'Curry Avenue.
There have been three arrests in the case so far but no charges.
Four days later, criminal John Wilson (35) was shot dead at his home in Ballyfermot, west Dublin.
One man has been charged with murder.
Gardai have also charged a man in relation to the gun murder of Shane Rossiter (30), who was shot dead at a house in Golden, Co Tipperary, on the morning of October 17.
A former garda who became involved in serious criminal activity was found shot dead at his rural home in Cornaveagh, Co Cavan, on November 9.
It is believed that John Kerins (49) was targeted by his former associates who were concerned that he might talk to gardai about their drug-dealing activities and other serious crime that they are involved in.
At the time of his murder, Kerins was facing a Circuit Court trial and a possible jail sentence if convicted of possession of stolen property charges, which were investigated by officers from Togher Garda Station in Cork.
The stolen plant machinery was worth more than €20,000 and the former detective was charged with stealing it in April of this year.
On December 4, so-called crime godfather Eamon Kelly (65, below), was shot dead close to his home in Killester, north Dublin.
A Dublin man has been charged with his murder and gardai have arrested six other people, including two women and a senior dissident Republican.
Just last night Christopher Warren (35), from St Teresa's Gardens, Dolphins Barn, became the 16th person to die a gun-related death in 2012.