Eyewitness Francis Crawford at the scene at Buncrana Pier in Co Donegal

People at the scene at Buncrana Pier in Co Donegal

A policeman stands guard at the cordon around the pier

The dead are all believed to be from Londonderry city

Police tape at the scene at Buncrana Pier in Co Donegal

Members of the public lay flowers at the scene of the incident

A Garda officer at Buncrana Pier in Co Donegal where five people died

Sean McGrotty, with his partner Louise holding their baby, four-month-old Rionaghac-Ann and his sons Mark, 12, and Evan, eight

A hero rescuer who saved a young baby from a pier side drowning tragedy that claimed five other lives has described how the infant's father chose to stay with his other children rather than save himself.

Davitt Walsh swam out into Buncrana harbour in north Co Donegal on Sunday night in an effort to reach the six people trapped in a car that had slid off the slip way into Lough Swilly.

Sean McGrotty, 46, died along with his two sons Mark, 12, and Evan, eight, his mother-in-law Ruth Daniels, 57, and her 14-year-old daughter Jodie Lee Daniels.

The only survivor was Mr McGrotty's four-month-old baby girl Rionaghac-Ann.

Mr Walsh described how the father handed him the infant out the broken driver's side window just moments before the Audi Q7 sank.

"The father looked at me and he had to make a decision," he said.

"He could have saved himself because he was out of the car but he went back into his family and I couldn't do nothing else, the car went down instantly and the whole lot of them went down, it was just so fast. I took the baby back to the shore."

In an interview with RTE, Co Donegal man Mr Walsh added: "I think the father knew that I was only going to be able to save one person and he said to me, the last thing he said, he handed her to me and he said 'save the baby' and he stayed and he went back in and he stayed with his family and the car just disappeared."

Mr McGrotty's wife Louise was away for a hen weekend when the tragedy unfolded.

The young mother who has lost her husband, two children, mother and sister has said her surviving baby is her reason to live.

Mrs McGrotty, from Ballymagroarty in Londonderry city, was in the family home for much of the day surrounded by extended family and friends as she tried to grasp the extent of the tragedy.

Clergy and politicians also came to express their condolences, including parish priest Father Paddy O'Kane who revealed the small mercy visited on the family.

"They are inconsolable," he said.

"Louise said to me, 'I have lost everyone, except little Rionaghac-Ann'. She said 'Rionaghac-Ann is my reason to go on'."

The baby girl is said to be doing well in Letterkenny General Hospital.

Gardai are treating the incident - one of the worst to hit the Inishowen area of Donegal - as a tragic accident.

Ms McGrotty's brother Joshua plays for Derry City FC.

The Daniels and McGrotty families thanked everyone who had supported them in the wake of the tragedy.

"Our families have been devastated by the tragic events of last night in which five members of our family died in a terrible accident," they said.

"The family has been inundated with support and sympathy from the local community and further afield and this is deeply appreciated."

President of Ireland Michael D Higgins joined Northern Ireland's First and Deputy First Ministers in extending sympathies to the extended families.

"I have heard with the greatest sadness of the terrible loss of life of a family in Buncrana," he said.

"My heart goes out to the family and loved ones."

Martin McGuinness, who visited the scene in Buncrana after visiting the grieving mother in Derry, said there were no words to sum up her heartache.

"I have just come from meeting a young woman who has lost her partner, her two sons, her mother and her sister and it is a very, very sad house," he said.

"Truly heartbreaking, mind numbing and shocking beyond belief."

He said the family were in a total state of shock.

"They are absolutely heartbroken," he said.

NI First Minister Arlene Foster issued a joint statement with Mr McGuinness to express sorrow over the deaths.

"This tragedy resonates with us all. At times like this it is difficult to comprehend how life can be so altered in the matter of moments," they said.

The Audi car driven by Mr McGrotty is believed to have been turning at the end of the pier in Buncrana when the wheels failed to grip.

The slipway structure, used by vehicles to access a ferry back and forth across Lough Swilly to Rathmullan in the summer, is prone to a build-up of thick algae.

Emergency rescue crews, including local RNLI lifeboats based on the Swilly, were on the scene within minutes of the alarm being raised by eyewitness Francis Crawford.

He said he watched Mr McGrotty scream for help as the Audi slid in to the sea off the pier.

"The man was still shouting to me when the car went down. It was very sad," he said.

"There was nothing I could do, or nothing anybody could do.

"Any of the people who could do something were coming as quick as they could and got here in great time and knew what to do.

"But it was all too late. There was nothing anybody could do. Everybody did what they could and it was too late."

Mr Crawford said he asked Mr Walsh to swim out as the car edged, nose first, into the water about 30m from shore and 12 feet of freezing water.

"How he got (the baby) ... they are saying it was handed out to him," Mr Crawford said.

"When he came back he was totally exhausted. I think if he had another five yards to go - I can't see how he would have made it."

Mr Crawford said Mr Walsh was a hero who had risked his life.

The pier is a very popular scenic spot, with hundreds of day-trippers visiting the area from Derry and the north west every weekend.

Mr Crawford described the panic that ensued with the car sinking within minutes of it sliding down the slipway.

"I was watching the car and the nose of it started to dip and then all of a sudden the whole of it started to go down, nose first, and everything stopped," he said.

A major air and sea rescue mission was mounted by the Irish Coast Guard, gardai and emergency services after the alarm was raised.

Two lifeboats, a helicopter and local fishing boats were involved in the efforts.

Mr Crawford broke down in tears recalling the final moments, and three of the occupants drowning after freeing themselves from the car.

"It was harrowing and heart-rending," he said.

"I don't want to go into details.

"Feeling hopeless and helpless. Nothing you could do and the man (driver) was shouting to me and I said 'I've phoned them, everyone is on their way' and he was still shouting.

"You felt so hopeless and you watched it unfolding in front of your eyes.

"It was a surreal sort of thing."

A book of condolence is to open in Derry and in local churches.