New York (CNN) -- A 10-year-old boy escaped out of the window of a sinking minivan after his mother drove the vehicle with her three other children into the Hudson River, some 60 miles north of New York City, authorities said.
Lashaun Armstrong swam to shore Tuesday night and was picked up by a passer-by and brought to a nearby fire station in Newburgh, New York, said Fire Chief Michael Vatter.
Soaking wet and suffering from a mild case of hypothermia, Armstrong then told fire officials his mother had driven the vehicle into the river.
Police divers later discovered the bodies of Lashanda Armstrong, 25, an 11-month-old girl, a 2-year-old boy and a 5-year-old boy some 25 yards off shore.
A police investigation into the incident suggests that the mother intentionally drove the vehicle into the water, according to Newburgh Police Chief Michael Ferrara.
Responders, using dive teams and a circling helicopter, found the van after an hourlong search submerged in eight feet of murky water, according to Vatter.
Before the incident, a relative called police reporting a "domestic disturbance" that police say may have involved Armstrong's husband, Jean Pierre.
That belief is based on a phone call the relative received in which they said they heard "tussling in the background," noting a history of domestic problems, police said in a statement Wednesday.
Police declined to identify the relative.
An autopsy on the four bodies is scheduled for Wednesday.
Newburgh Mayor Nicholas Valentine said the incident is certain to have "a lasting effect on this city."
City resident and neighbor Christine Santos said she "would never have imagined (Lashanda) to do this to her kids."
"To them little babies. I would have never have imagined. I'm in shock," she added.
Other neighbors described her surviving son, Lashaun, as responsible.
"He was the type of kid that was responsible for his little ones," said resident Carmen Davila.
But the traumatic effects of Tuesday's incident could have long-term effects on the boy, analysts say.
"He has this major traumatic event and loss and that can be manifested in many ways," said Dr. Louis Baptista, director of Columbia University's Clinical Services for Child and Adolescent Psychiatry.
He warned of "aggressive behavior, through violence, through depression, through depressive symptoms and that can be quite severe and quite impairing in a child his age."
CNN's Deb Feyerick and Sheila Steffen contributed to this report