A 2-year-old Northern Virginia boy died Friday after being found unresponsive in the family minivan, where he might have been left for hours, authorities said.

The toddler was found by his mother about 4 p.m. in the vehicle on Gentle Shade Drive in the Bristow area of Prince William County, a county police spokeswoman said.

The child was reportedly last seen alive about 9 a.m., police said. They identified him as Ryan Murphy and said he would have been 3 next month. His parents’ names were not released.

The minivan was in the driveway of the family home when the child was found, said 1st Sgt. Kim Chinn, a police spokeswoman.

She said the cause of death might have been heat-related. “It appears” that the child was in the vehicle all day, Chinn said.

Temperatures in the area were in the 70s and low 80s Friday. It was cloudy for part of the day.

After the discovery of the child, the mother’s screams attracted the attention of a neighbor, a retired or off-duty police officer, Chinn said.

The officer administered CPR, according to Chinn, but apparently to no avail. She said the child, who had been in a car seat, was pronounced dead at a hospital.

“I know she wasn’t neglectful,” a neighbor said about the boy’s mother. “She loved that boy.

“It’s horrible,” said the neighbor, Marian Lofton. “Here you have a woman who’s so caring. . . .” Lofton said residents of the neighborhood, a half-dozen miles west of Manassas, were trying to decide how to support the child’s mother. “We’re in shock,” she said.”We’re all in shock.”

Many details of the incident remained unclear Friday evening.

It was “still early” in the inves­tigation, and authorities “have ­really distraught people” to speak with, Chinn said.