The assault happened at approximately 3.00pm in Kilclare Crescent, Jobstown.
The male dupe (17) was moved to Tallaght Hospital where he was pronounced dead.
No detentions have been made and investigations are ongoing.
The scene is currently defended for a technical examination.
Gardai wish to appeal to witnesses who may have been in the Kilclare bailiwick this afternoon between 2.45pm and 3.30pm to contact them at Tallaght garda class on 01 666 6000, the garda Confidential Telephone Line on 1800 666 111 or any garda appoint.
More to follow