Attackers kicked in the door of a house in west Dublin before shooting dead a father of three last night.
Gardaí are looking for two or three people involved in the murder of 35-year-old Darragh Nugent.
They are appealing for information from anyone who saw an old saloon car, possibly a BMW, leaving the scene at Wheatfield Drive at around 9.40pm yesterday evening.
Most of the attention around the crime scene this morning was from local children passing on their way to school.
A forensic examination is being carried out at the scene.
Photo: Sam Boal/RollingNews.ie
Neighbours report having a heard a number of shots last night.
The victim is understood to be known to gardaí, and the murder may be the result of a local feud.
Gardaí do not believe it is connected to the Kinahan-Hutch gangland feud in the city.
Superintendent Dermot Mann from Lucan Garda Station explained: "We believe that the confrontation and the shooting happened out on the street.
"This is a father of, I understand, a number of small children - and that makes it all the more horrific."
Anyone with information can contact Roanastown Garda Station on 01-666-7700.