The family, who have been living in IL in the U.S. for a number of years, had rented a auto at Shannon Airport and were travelling in convoy to the home of Winnie Keevey, where her wake was being held.
Stephen Alexander was a police officer for the Bolingbrook Police Department, the Chicago Tribune reported. "Steve will be missed by all those who had the pleasure of knowing him and we will forever keep the Alexander family in our thoughts and prayers".
Steve Alexander had two daughters, aged 11 and 10.
A statement from Bolingbrook Police Department in IL said father-of-two Steven (49) had served with the force for 17 years.
"He also enjoyed racing his vintage Camaro drag racing auto and talking to children about vehicle and driving safety".
Tributes have been paid to the tragic family of four after the tragedy has left the community "numb".
A section of the road has been closed off since last night and diversions from the N25 will remain in place until lunchtime at least.
The cause of the collision is not known and it is understood road and weather conditions were reasonably good in the area at the time of the crash.
The investigation is continuing.