Five people, including three children, who died after a car went off a pier in County Donegal, in the Republic of Ireland have been named locally.
They were Ruth Daniels, 57, her daughter Jodie Lee Daniels, 14, Sean McGrotty, 49, and his sons Mark, 12, and Evan McGrotty, eight.
A four-month-old baby girl was rescued by a passer-by, she is in a stable condition in hospital.
They died after their car entered the water at Buncrana on Sunday.
Jim McGrotty, a brother of Sean, said they've all been living a nightmare since news of the tragedy unfolded.
Supt Colm Nevin told a press conference at 12:00 GMT on Monday that they are treating the incident as "a very tragic accident".
"I would like to thank the public who came to the assistance of these people last night in their time of distress, particularly the local person that took the baby from the vehicle," he said.
"No doubt he did display exceptional bravery."
'Grab the baby'
One shocked eyewitness, Francis Crawford, told BBC Radio Foyle he felt "helpless".
"I phoned 999, I explained there was a car in the water and there's a family in it that's going to be sinking," he said.
"A fella came over and I asked him if he could swim, he stripped off to his underwear and headed out and it was great that he did.
"He was totally exhausted, I think if he had another five yards to go I don't see how he could have made it.
"He was shouting 'grab the baby, grab the baby'. He was taken to hospital, he was cut and different things but very heroic and he saved the wee baby's life."
"All the time the car was bobbling about," Mr Crawford said, "and I was hoping against hope that the car would stay up until the people came.
"I was watching the car and the nose of it started to dip and then all of a sudden the whole car just went down nose first and everything stopped. It was harrowing and heart wrenching... feeling hopeless and helpless, nothing you can do."
John McCarter of the RNLI said it was a harrowing scene.
"It's an absolutely tragic happening here," he said.
"I have never witnessed anything on this scale in Lough Swilly in my lifetime - just the sheer scale of it and the fact that it has happened just literally on our shoreline.
"But then, when you are dealing with the sea, it doesn't really matter where you are. It's a dangerous place.
"It is a very distressing thing to deal with any kind of tragedy, but particularly where children are involved."
Sinn Féin councillor Jack Murray said questions are now being asked as to whether the car entered the water because of the pier's slippery surface.
"It seems to be the case that the car was trying to manoeuvre and it then started to slip down on algae and it started to go into the water.
"I live very close to the pier, there were close to 100 people there hoping for better news than they got.
"There was a helicopter out on the (Lough) Swilly, it did a spotlight search and it became clear fairly soon that there wouldn't be survivors."
Buncrana councillor Rena Donaghy called it "a tragedy of enormous magnitude".
"It's hard to take in that just a matter of hours ago, Buncrana was buzzing with people who were down from Derry and beyond to enjoy the lovely weather," she said.
"It was so scenic and happy and now happiness has turned to tragedy."
The Irish Coastguard launched a major search and rescue operation after what it described as a "tragedy".
The coastguard helicopter and local fishing boats were involved in the rescue. Police, ambulances and fire brigade also rushed to the scene.
Northern Ireland's Deputy First Minister Martin McGuinness, who has visited the victims' family, said there were "no words to describe such a horrific incident".
"I had a very sad duty this morning to visit the family and speak with a young woman who has lost her partner, her two sons, her mother and her sister and it was heartbreaking to be there.
"The only consolation out of this is the heroism of the man from Kerrykeel, who swam out and saved the baby," he said.
"The reports are very, very good about the baby but it was really a very sad scene at the home this morning."
The Mayor of Derry City and Strabane district council, Elisha McCallion, said she would be opening a book of condolence in the coming days.