Authorities are now classifying the deaths of a mother and her 3-year-old son in a house fire in Scotch Plains as a homicide-suicide. Katherine Halverson, 32, and her son, Jeremy Scott McDonald Jr., were at first thought to have died after getting caught in the fire in their home Tuesday night.

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SCOTCH PLAINS — Authorities are now classifying the deaths of a mother and her 3-year-old son in a house fire in Scotch Plains as a homicide-suicide.

Katherine Halverson, 32, and her son, Jeremy Scott McDonald Jr., were at first thought to have died after getting caught in the fire in their home Tuesday night.

But following an autopsy conducted this morning, authorities now say Halverson took her son to a small second-floor bedroom, where she set fire to the room, Union County Prosecutor Theodore Romankow announced this afternoon. The county homicide task force is investigating with Scotch Plains Police, and no possible motive for the killing was announced.

At a press conference late this afternoon at Scotch Plains Police headquarters, Police Chief Brian Mahoney said Halverson "placed material, like rags in front of the door then poured an accelerant on the rags and lit them on fire." He said the fire was contained to one side of the door, and was easily doused.

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An autopsy on Halverson and her son revealed both died of smoke inhalation, more specifically from asphyxiation due to inhalation of combustible materials.

The mother and child were found in the same bedroom shortly after 7:15 p.m., when the fire department was first dispatched to the home on Church Avenue.

The family dog, which also died, was found in the same bedroom, authorities said.

Their deaths were initially something of a mystery because Investigators said the fire left few signs of its deadly power, and neighbors reported they saw no flames, only smoke.

Halverson attended Scotch Plains-Fanwood High School, for which she played wide receiver on the varsity football team in the mid-1990s.

She was at the time one of three girls playing on New Jersey boys’ squads and routinely completed two-hour practices – despite, she said, the boys’ teasing.

''This means a lot to me,'' she said in 1995. ''I'm making history at my school and when I look back on my life, I'll know I did something.''

Her coach, Steve Ciccotelli, at the time praised her for her determination.

''I admire her heart for attempting this,'' Ciccotelli said. ''I think it's the hardest game anyone can play.''

In photographs posted on his parents' respective Facebook pages, their 3-year-old Jeremy looks both charmed and intrigued by the world around him. In a different photo posted Tuesday on Katherine Halverson's Facebook page, Jeremy is wearing a red-and-blue striped sweater and sporting a Santa hat.

The two-family house on Church Avenue in which the two lived, along with possibly one or two other relatives, looked relatively unscathed from the street this afternoon.

But the side-by-side doors were cordoned off with yellow police tape — and the two second-floor windows at the front of the house were boarded up. Otherwise, there appeared to be no damage, with the windows on the same floor intact.

Neighbors were surprised at the lack of fire they saw coming from the house.

“It was only smoke,” said Joyce Ruffin, who lives two doors down. “I said ‘Where’s the fire?’”

On Tuesday night, township police Chief Brian Mahoney said neighbors reported seeing smoke coming from the second floor of the duplex-style home at 1918 Church about 7:15 p.m.

Firefighters forced their way into the home and up to the second floor, he said.

The small fire was extinguished within five minutes, Mahoney said, adding that all of the damage was confined to the second floor of the victims’ apartment.

Halverson and her son were taken to Overlook Medical Center in Summit where they were pronounced dead. The family’s dog died at the home.

Late Tuesday night, shards of glass from two second-floor windows were scattered over the top of an enclosed first-floor porch. A large Christmas wreath, adorned with a red bow and lights, hung next to the windows. More lights were strung under the eves.

Star-Ledger staff writers Seth Augenstein, Richard Khavkine, Tomas Dinges and Alexi Friedman contributed to this report.

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