A man and a young boy killed in a horrific head-on car crash have been named.
They are Vincent Rossi (30) and his son Sully (5).
Both died when their car was involved in a collision with an articulated lorry in Co Offaly on Monday evening.
Emergency services described the crash scene at Tullamore as one of total "carnage".
Mr Rossi's daughter, Hayley (9), and another son, Daniel (8), were also in the car at the time of the crash.
Hayley was airlifted to Crumlin Children's Hospital with serious injuries.
She was last night said to be in a critical condition and was due to undergo emergency surgery.
Daniel was also seriously injured and was taken by ambulance to the Midland Regional Hospital, Tullamore.
The family live in Portlaoise, Co Laois.
Neighbours described Mr Rossi as a devoted father and a caring neighbour.
"He was always so friendly and very funny," said one neighbour. "He was a great father.
"The kids were always playing outside together."
Another neighbour said Mr Rossi helped her when she moved into the area.
Garda Superintendent Tom Mullarkey said gardai are appealing to anyone who stopped at the scene of the accident to come forward.
He told the Herald that some witnesses had already contacted gardai, and appealed to others to do the same.
The officer, who described the crash as the worst he had seen in 37 years' service, said a team of investigators is trying to determine what led to the accident.
"It was an absolutely chaotic scene. It was truly horrible," he said. "Two members of the same family have died - a father and his five-year-old son.
"Meanwhile, two other children are in hospital.
"Both are receiving treatment for serious injuries.
"We have quite a few people who have come forward to give us their details about one thing or another.
"But there are a number of people, a number of motorists, who stopped before continuing on.
"The other thing I am asking is that a number of people stopped here in the immediate aftermath of it and helped the emergency services.
"When some people finished they felt they weren't needed anymore. We are looking for those people to come forward, too.
"We have had a team of forensic investigators here. Normally, we need only one at a fatal accident, but we had a team here and they will determine how this happened."
Parish priest Fr John Stapleton said the tragedy was "very frightening for a community".
He said he had been nearby on Monday night and saw a helicopter arrive.
He said he had prayed for the first responders and medical teams who helped the victims.
"God help the family with what they have to cope with right now. And then the first responders, I think they are a group sometimes forgotten, and gardai and medical people, and the fire brigade," he said.
A major emergency response operation was launched after the crash on the N80 Tullamore-Mountmellick road at 5pm on Monday. It was reopened yesterday morning.
The driver of the lorry suffered minor injuries.