The 10-year-old who swam ashore as his mom and three siblings drowned in a sinking minivan says his mother told her kids, "You're all going to die with me," then changed her mind and tried, too late, to back out of the frigid Hudson River, according to the woman who found the sopping wet boy.

Meave Ryan was driving past the boat ramp in Newburgh on Tuesday evening when she spotted La'Shaun Armstrong waving his arms.

Meave Ryan was driving past the boat ramp in Newburgh, N.Y., on Tuesday evening when she spotted La'Shaun Armstrong, 10, sopping wet, waving his arms. ((Mike Groll/Associated Press))

Ryan said the boy told her that his mother, Lashanda Armstrong, had a "big, big argument about my stepdad's cheating on her," then piled her four children in the minivan and sped into the river.

Ryan told The Associated Press on Thursday that the boy said Armstrong had held the kids as the minivan began sinking.

"She was holding on to all of them and said, `If I'm going to die, you're all going to die with me.' She said that two or three times," Ryan said.

But as the vehicle sank, La'Shaun broke free of his mother's grasp and clambered out a window.

Ryan said: "While he was doing that, he heard his mother saying, 'I made a mistake, I made a terrible mistake.' And she tried to reverse the car out, but at that time it was too late. He said, 'Mommy, I'm going to go get help,' and she said, 'OK.' And that was the last he heard from his mother."

Ryan drove the boy to a nearby fire station. Rescuers immediately went to the river, but it was too late: They found the van about 25 metres from shore in 2½ metres of water. Lashanda Armstrong and three children — ages 11 months, two and five — were dead.

Ryan's account conforms to reports from police, who say Lashanda Armstrong was involved in a domestic incident at her apartment Tuesday evening and within minutes had plunged off a boat ramp into the river less than a kilometre from her apartment in a hard-luck section of the city.

"I don't know if we'll ever find out what Lashanda Armstrong was thinking when she left that home and drove to the river," said Newburgh police Chief Michael Ferrara.

Minivan sped toward river

Lt. Bruce Campbell said police had heard from at least two witnesses who said they saw a minivan speed through an intersection at the boat launch's entrance fast enough that the vehicle appeared to bottom out on the bumpy pavement.

"She went through it at a pretty good pace," Campbell said. The witnesses, motorists who had stopped at a stop sign, "just thought it was kids driving fast or acting up." They apparently didn't see what happened next, he said.

Campbell said police believe she hit the water going 25-30 km/h. There was no substantial damage to the vehicle's front end, and the airbags didn't deploy, he said.

A stream of people went to the boat ramp Thursday and friends and neighbours gathered to try to process the tragedy.

Ashonti George, 21, of Newburgh, laid a single red rose on the doorway to Armstrong's apartment Thursday morning. The two women were in the same math class at Orange County Community College. George said that Armstrong usually was an attentive student but wasn't herself during a Tuesday morning test.

"She was off," George said. "She didn't seem like herself. She seemed angry — off. That's the best way I can explain it."

Armstrong's aunt had called police at about 7:45 p.m. Tuesday to report a domestic incident at her niece's apartment. By the time police got there, she was gone. Besides Armstrong, Landen Pierre, 5, Lance Pierre, 2, and 11-month-old Laianna Pierre died.

Earlier that day, Armstrong appeared stressed when she picked up the children at the Young and Unique Christian Development Child Care, said Shaniesha Strange, supervisor in the infant room.

Police questioned the man they identified as the father of the three dead children, Jean Pierre, but did not give details. He apparently didn't live with the mother and children and could not immediately be located for comment.