Gardai have said a 39-year-old man shot dead at a house in north Dublin this morning had been warned five days ago that his life was in danger.
The Minister for Justice, Michael McDowell, earlier said an intensive garda operation into the activities of the criminal who was murdered may be the reason he was targeted.
Martin 'Marlo' Hyland, 39, was shot dead this morning as he slept in the home of a relative in Scribblestown Park in Finglas.
A 20-year-old apprentice plumber, Anthony Campbell from St Michans Flats in Dublin, was also shot dead.
He had been working in the house at the time and gardaí said he was 'in the wrong place at the wrong time'.
It is believed that an older man, a plumber who was working with the apprentice, left the house before 9am to get some materials.
Following this the killer or killers arrived and shot the apprentice who was downstairs before moving upstairs and shooting Mr Hyland.
The other plumber arrived back at the house at about 10am and alerted gardaí.
Mr McDowell has called the killers 'ruthless savages' and said his heart goes out to the Campbell family.
Mr Hyland was described as one the biggest drug dealers in the country and was involved in heroin and cocaine trafficking, gun smuggling and was linked to a number of shootings and murders.
He was the target of the garda operation 'Oak' and investigating gardaí investigating have previously arrested 30 associates and seized over €15 million worth of drugs.
The Minister for Justice also said the killings were a very serious development and that gardaí were shaken by it.
Mr McDowell said that said it was clear that even though Mr Hyland was not in his own home, he had been under surveillance and that his killers had put in a good deal of preparation.
The Garda Commissioner, Noel Conroy, has appointed Assistant Commissioner Martin Callinan, head of the National Support Services, to lead the murder investigation.
Gardaí have appealed for motorists or anyone who saw anything at the junction of Ratoath Road and Scribblestown Park between 9am and 10am this morning to contact them.
They also want to hear from anyone who saw a black Volkswagen Passat (06 D 77432) which was found burned out near the Quarry Pub in Ballygall Road in Glasnevin.