The three sisters were taken by ambulance to Children’s Health Ireland (CHI) in Crumlin and were later pronounced dead. Two were children while the third was an adult teenager. A teenage boy was also taken to Tallaght Hospital with serious injuries which are not thought to be life-threatening.
The mother of the children, who was not injured at the scene, was also taken to CHI and is receiving medical treatment.
Gardai were informed of the incident and arrived at the scene at approximately 12.30am on Sunday, September 4.
The Garda Armed Support Unit arrested a man in his early 20s at the scene.
He is currently detained at Tallaght Garda Station under Section 4 of the Criminal Justice Act 1984.
Gardai said everyone involved is believed to be known to each other and officers are not looking for anyone else in connection to the incident.
An incident room has been established in Tallaght Garda Station and all the circumstances are being investigated under the direction of a senior investigating officer.
The scene in Rossfield Estate remains sealed off and a forensic examination will take place on Sunday by the Garda Technical Bureau.
The Coroner’s Office and the Office of the State Pathologist have been informed. Post-mortem examinations will also take place.
Gardai have appointed a family liaison officer and will continue to support those involved in conjunction with other state agencies.
A Gardai spokesperson said: “This violent, challenging and traumatic incident was responded to by uniform unarmed Garda first responders from Tallaght District, supported by uniform members and armed detectives from the wider DMR South Division and Specialist Armed Support Unit members.
“An Garda Siochana has put in place welfare supports for, and will continue to support, all members who attended this incident.”