Inside with her were the boy's siblings: two boys, ages 5 and 2, and an 11-month-old girl.
Firefighters and police officers responded with boats. Divers searched for the minivan for about an hour before finding it submerged in 10 feet of water about 25 yards offshore. They used a heavy-duty tow truck to pull it up the boat ramp and onto land.
Everyone inside was dead, Vatter said.
The woman lived about six blocks from where she and her children perished, he said. Their names have not been released.
The domestic altercation occurred about 10 minutes before the woman drove into the river, said Vatter, who didn't have any more information on it.
Newburgh, which has about 30,000 residents, sits on the western shore of the part of the river that runs south through New York state and eventually splits New York and New Jersey.
The killings are reminiscent of the case of a South Carolina woman who drowned her young sons in 1994.
Susan Smith is serving a life sentence for killing 3-year-old Michael and 14-month-old Alex by strapping them into their car seats and driving the car into a pond. Smith originally claimed she was carjacked before the truth came out.