Police say other children witnessed the alleged attack on Mark Mason, who died at the scene

A Pennsylvania man is under arrest and charged with fatally stabbing the 8-year-old son of his girlfriend in an attack watched by other children.

“Die!” the others heard him say, according to a criminal complaint in the case, reports Pittsburgh TV station KDKA.

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Pennsylvania State Police Trooper Jim Long tells PEOPLE the incident unfolded about 10:30 p.m. Monday as the suspect, 43-year-old Keith Burley, was riding in a car in New Castle with his 36-year-old girlfriend and two of her children, a 7-year-old and the 8-year-old victim, Mark Mason.

Image zoom Keith Burley Pennsylvania State Police

“She was actually driving the car,” he says of the woman, when an argument ensued that “became physical.”

After the woman stopped in front of the New Castle fire station and she got out to seek help, Burley took over the vehicle and drove off to the woman’s house, he says.

Inside the home, two more boys, an 8- and a 15-year-old who were playing video games upstairs, heard someone enter and went downstairs to find Burley with the other two boys, according to the criminal complaint cited by New Castle News.

Burley allegedly held a gun and instructed the boys in the home to go find a magazine that held bullets for the weapon, according to the police report.

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As they were returning from a bedroom, the 15-year-old said he witnessed what appeared to be Burley hitting Mason. As the two brothers drew closer, they saw him allegedly stabbing Mason with what the other 8-year-old described to police as a pink camouflage knife.

“They fled the house,” says Long. “They went to a neighbor’s house and they called 911 from there.”

Burley also fled before officers arrived. The boy was pronounced dead at the scene.

One of the brothers who flagged down police told them “Bud,” a nickname for Burley, had stabbed his brother, reports New Castle News.

After a manhunt in which state police described him as “armed and dangerous,” Burley was located around 9 a.m. Tuesday about 20 miles away across the state line in Youngstown, Ohio, and apprehended without incident with help from the U.S. Marshal’s Service, says Long.

He confirms that Burley was on parole after his March release for a previous homicide conviction. He had pleaded guilty to third-degree murder and having a gun without a license during commission of a 1999 robbery, according to New Castle News.

“It tears you up,” Joan Stewart, who lives across the street from where the stabbing occurred, told KDKA. “I don’t believe it. How could anybody stab a little kid?”

Felony charges accuse Burley of criminal homicide, aggravated assault, simple assault, kidnapping, terroristic threats, reckless endangerment and unlawful restraint.

He currently is being held in the Mahoning County, Ohio, jail, awaiting extradition to Pennsylvania, online jail records show. An attorney who might speak on his behalf was not identified.