Gardaí are now preparing a file for the Director of Public Prosecutions.
However, a second male has been arrested.
The youth is in his late teens and is being held at Templemore Garda Station under Section 4 of the Criminal Justice Act, 1984.
The fatal hit and run incident occurred on Saturday at Ballyhiskey, Carrigatoher, Nenagh, Co Tipperary.
A man in his 60s was killed in the two car crash.
He was taken by ambulance to University Hospital Limerick where he was later pronounced dead.
The front seat passenger in his car, a woman in her 60s, was also brought to hospital, where her injuries are non-life threatening.
Investigations are continuing.