He was enjoying his Easter holiday break in a village in Co Cork when he was hit by a car which failed to stop around lunchtime yesterday.
His family were keeping a bedside vigil at Cork University Hospital (CUH) last night as doctors were doing everything they could to keep him alive.
Gardaí were alerted just before 1pm yesterday when the child was knocked down in the village of Ballymacoda, near Youghal.
He was rushed to hospital and gardaí immediately started looking for the driver of the car involved.
They also sealed off the area for technical examination and carried out inquiries in the village.
About an hour later they spoke to the driver of a vehicle who was of interest to them. He was later formally arrested for questioning at Midleton Garda Station.
It is understood that he is in his late 40s and comes from the Ballymacoda area.
The boy, who hasn’t been named, is believed to have moved into the village recently with his family.
Supt John Quilter, who is leading the Garda investigation, said they want to hear from anybody who was in the village from 1pm to 1.30pm yesterday and saw the incident.
* Anybody with information is asked to contact Midleton Garda Station at 021-4621550.