Five members of the same family were killed after their car plunged into the water at Buncrana pier in Donegal.
It's understood that a couple and three of their children were killed in the horrific accident at around 7.15pm yesterday.
A fourth child was pulled to safety by local people who jumped into the water at Lough Swilly when the family's Audi Q7 4x4 appeared to tumble off the slipway.
The children who died were of national school age, said one eye-witness.
"It was the most awful scene," said another local man.
"The emergency services worked tirelessly to try to rescue the family but there was little they could do other than to try to recover them from the water as quickly as possible."
A major rescue operation swung into action immediately.
The Sligo 118 Coast Guard helicopter and RNLI crews from the town and from Greencastle assisted gardai and ambulance crews at the scene.
The vehicle was pulled from the water just after 9pm.
The child who was rescued was rushed to Letterkenny University Hospital by an ambulance crew.
Local people say there had been a number of incidents in recent months of cars parking on the slipway and getting into difficulty.
The slipway has been covered in a thick layer of algae.
Gardai sealed off the scene and a full investigation into the tragedy was to begin at dawn today. Dozens of locals gathered at the pier last night as the operation to recover the bodies continued.
Local councillor Jack Murray told the Herald that emergency services were quick to act.
"I live directly on the pier at Buncrana, and heard the first sirens at around 8pm," he said.
"It was only when we heard several more in the next half an hour that I realised there was something very serious happening.
"A large crowd of around 200 people were gathering along the pier, they are absolutely devastated because the extent of the tragedy had become apparent.
"Dozens of gardai and other emergency services were at the scene. It's truly shocking, my thoughts are with the people and their families," the Sinn Fein councillor added.
Eye witnesses described the scene as "absolutely manic" as emergency services rushed to the scene in an attempt to save a number of people in the water.
"There were dozens of gardai, fire units and water rescue teams around the pier. They were focusing their attention on one particular area of water," one eye witness said.
"They managed to pull one small child out in time, but it doesn't seem like they got to anybody else in time."
The victims may have been visitors to the town. The pier is a popular stop-off point for tourists and locals alike.