A man and two children aged five and seven have been taken to hospital following a lightning strike in Lisburn.
It happened on Tuesday afternoon at around 1.50pm on the Laurel Hill road. The man was collecting his children from Killowen Primary School.
Witnesses said he was on his mobile phone at the time of the strike. He was taken to Lagan Valley Hospital.
A spokesman for the South Eastern Health Trust said the man was "critically ill".
The two children, a boy (5) and seven-year-old girl, are in the Belfast Children's Hospital for treatment to burn injuries.
The Belfast Trust said the boy is in a critical condition. The girl who was seriously injured is now in a stable condition.
It is understood the 37-year-old man and his family had been making their way towards their jeep when the lightning struck.
School staff gave emergency medical assistance, with the vice principal using a defibrillator on the critically ill father.
At the scene - a gravel sports pitch -- there was little sign of the tragedy which had unfolded just hours earlier.
The extensive police cordon was lifted just before 5pm.
The principal of Killowen Primary School in Lisburn, Fiona Douglas, said: "I can confirm that a parent and two children were injured outside the school’s main gate this afternoon.
"School staff and parents attended to the injured family until the arrival of the emergency services. Following this all other pupils, accompanied by staff, went safely to nearby Laurel Hill Community College where they were collected by parents.
"The thoughts of the entire school community are with the family at this time."
Community 'stunned by absolute tragedy'
SDLP Lisburn Councillor Pat Catney said that the local community is stunned following the incident.
Councillor Catney said: "This is an absolute tragedy. My thoughts are with the man and his son who have been taken to different hospitals in a critical condition. I also understand that the man’s daughter has been taken to the Royal Hospital where she too is seriously ill.
"There’s no preparing for an incident of this nature. I want to put on the record my sincere appreciation for the speed with which the ambulance service responded as well as the great efforts of teachers and parents to make the area safe for other children at the school.
"My prayers and the prayers of this entire community are with the family at this very difficult time."
'You never imagine it's going to happen in your local town'
Lagan Valley MP Jeffrey Donaldson said: "From what I'm hearing the situation is pretty grim and our thoughts and prayers are with the family. it must be devastating news to be told that three of your loved ones have been struck down in such a cruel way and we can only hope that there is a recovery from this in every sense of the word.
"I guess we often read about these things but you never imagine it's going to happen in your local town. I think it's a stark reminder that even the weather can have terrible consequences at a time when people are reasonably happy that we've had a good spell of weather and when something like this happens it reminds us that mother nature is a very powerful thing."
Mr Donaldson has spoken to some of the parents at Killowen primary school who were also picking their children up from the sports day.
"Some of the children witnessed the aftermath of the incident and I know that the paramedics did a really good job and the school community at Killowen is a very strong community and I know that the staff and the parents will rally around and support the children in what must be a very traumatic experience for them."
Speaking from Stormont, Deputy First Minister Martin McGuinness has said his thoughts were with the affected family.
School staff and other parents must be commended
Former firefighter and Ulster Unionist Lagan Valley MLA Robbie Butler said: "Obviously all our thoughts are with the family who have been severely hurt in this freak accident. I hope and pray they make a full and speedy recovery. My deepest sympathies are with the three people that have been injured and I am sure they will be supported by the local community who will assist the wider family at this terrible time.
"Support for the family and school friends is also essential to ensure that all of those affected receive care and counselling. School staff and other parents must be commended for their actions in offering care until the emergency services could attend.
"As a former firefighter, I know it is important at these times to remind the general public of some important safety messages when an electrical storm occurs."
Ambulance service urges caution
The Northern Ireland Ambulance Service is urging caution following the incident.
It said in a statement: "As more thundery showers are forecast with the possibility of lightning we would ask people to remain very vigilant when they are out and about.
If there is a high chance of thunder storms – lightning safety advice would suggest that you stay indoors but if you are outside you should avoid open fields and hilltops.
"You should also stay away from tall, isolated trees. If you are in a group, spread out to avoid the current travelling between group members. You should also stay away from water and wet items as well as metal objects, which are all excellent conductors of electricity."
The Belfast Trust said that anyone who feels they could have been hit by lightning should seek medical advice.
Northern Ireland has been basking in sunshine for the past week, but there were warnings of heavy rain and thunderstorms for parts of the region on Tuesday.
On Monday, thousands of homes were left without power following lightning strikes in the Republic.
Before a thunderstorm
During the thunderstorm
After the thunderstorm