The 27-year-old was considered a “significant independent operator”, but Garda sources said he had kept “a low profile” in the past year-and-a-half in terms of drug trafficking and gun running.
Mr McDonagh was shot up to six times by two killers at his home in Clondalkin, west Dublin, just before midnight on Tuesday.
The assassins broke into his house and shot him at least once in his upstairs bedroom, where he was with his girlfriend.
He managed to escape out the window onto a front porch before landing on his car and falling to the ground.
The gunmen pursued him outside and fired a further four or five shots into him at close range with a handgun.
Garda sources said Mr McDonagh had been in a “few rows” in recent times, although gardaí are not sure how serious those disputes were. Detectives will investigate these incidents and try to identify the other parties involved.
Mr McDonagh was from Crumlin on the southside of the city and had moved with his partner into 45 Woodavens Estate, Ronanstown, a few years ago. He then built on a new house, 45a, on his side garden, which the couple moved into.
Garda sources said Mr McDonagh had in the past engaged in criminal activities with both sides of a violent gangland feud in the Crumlin-Drimnagh area, but gardaí are satisfied the shooting is not linked with that.
McDonagh has been linked with some of the country’s biggest drug traffickers, including murdered Finglas boss Marlo Hyland and a Tallaght trafficker based in Co Kildare.
Mr McDonagh was arrested in relation to a large drugs seizure on the Naas Road two years ago, but was never charged. This led to some suspicions he may have provided information to gardaí.
Investigators will examine this line of inquiry, but do not, as yet, believe it is the most likely motive.
Officers will also investigate if there is a link with a fight McDonagh had with a relative of a jailed crime boss two years ago, after which he was threatened.
Mr McDonagh was targeted by the Criminal Assets Bureau four years ago and they found €40,000 in the home he lived in at the time. He paid €60,000 in a final tax settlement. Senior sources said he had kept a “low profile” since then.
Mr McDonagh has operated a second-hand car business on the Naas Road in recent years.
Speaking at the scene earlier yesterday, Superintendent Pat Clavin declined to comment on possible motives: “At this stage it’s too early to say. A number of lines of inquiry are being pursued.”
He said that between 11.45pm and 11.50pm on Tuesday a dark-coloured saloon car, believed to have had a taxi sign on its roof, pulled up near the house. He said one of the men was described as being 5ft 10in to 5ft 11in, wearing dark clothes and well built, while the second man was slightly shorter and of average build.
“They forced their way into the house. The victim was upstairs in the bedroom. At least one shot was fired in the bedroom. The victim escaped through the front window out on to the porch roof and onto the bonnet of his car. The two culprits emerged from the front of the house and a number of shots were fired at the victim in the front of the house.”
He said the victim was pronounced dead at the scene. Supt Clavin appealed to anyone with information to contact the incident room at Ronanstown on 01 6667711 or the Garda confidential line on 1800 666 111.
CHRISTOPHER McDonagh is the 13th gangland-style killing in 2008.
Paul ‘Farmer’ Martin, 39, of Kippure Park, Finglas, shot dead in a pub in the north Dublin village. A significant drug dealer and armed robber, Martin was a target of a number of criminals.
Trevor Walsh, 33, shot dead near his home in Finglas. A recovering heroin addict, he was not considered a significant criminal.
Antony Foster, 34, of Cromcastle Court, Kilmore, north Dublin, shot dead as he left his flat. A convicted drug dealer, gardaí suspect his death was linked to a drugs gang.
Darren McGrath, 31, originally from Cork, was shot dead at Kilconny Estate, Belturbet, Co Cavan. A man has been charged in relation to the case.
Anthony Russell, 30, was gunned down as he sat drinking with friends in the Ardlea Inn, Artane, Dublin. His murder may be linked to a violent feud in the north inner city.
James Cronin, 20, of Ballinacurra Weston, Limerick, found in a shallow grave near Hyde Road, Limerick. He had been shot in the head. Gardaí believe his killing was feud-related.
Mark Moloney, 40, shot dead in the street in Limerick’s Garryowen area. Gardaí believe his murder was feud-related. One man has been charged with the murder.
Richard McCormack, 29, of Ronan’s Close, Ronanstown, Dublin, shot dead in Ronanstown. A drug dealer, gardaí believe his killing was in revenge for a fatal shooting the previous year.
John Berney, 29, and a father of four, shot dead at his home in Castlelyon Drive, Newcastle, west Dublin. A known drug dealer, gardaí believe his killing was drug-related.
Darren Guerrine, 21, of La Touche Road, Bluebell, south Dublin, shot in the head on the banks of the Grand Canal close to his home. A minor criminal, gardaí suspect his killing was drugs-related.
Andrew Burns, 27, of Strabane, Co Tyrone, brought across the border in a car into Donegal and shot dead on a roadway in the village of Castlefin. Gardaí suspect he may have been killed by dissident republicans.
David Lynch, 39, shot dead at Collery Drive, in Sligo town. A convicted armed robber, gardaí believe his murder was connected to a dispute between criminals in Sligo.