A woman was fatally stabbed while yelling “Stop! Stop!” and her teenage son was badly hurt after her beau allegedly attacked them with a knife Saturday morning in the Bronx, cops said.

Yesenia Hall, 42, was stabbed in the neck and torso and her 16-year-old son in the neck and back around 6:30 a.m. in their apartment on Sherman Ave. in Highbridge, according to police.

Next door neighbor Shantrice Diamond, 17, said she was half-asleep when she heard screaming and the sound of something heavy, like a dresser, falling.

“I heard the boyfriend yelling, ‘I’m gonna stab you,’” the teen recalled. “I heard the woman’s voice. She was screaming in pain. She was screaming, ‘Stop! Stop!’ After that she said, ‘I am gonna die, I’m gonna die’ and like two minutes later I heard nothing but silence.”

When Diamond heard the “horrific” screams, she woke her mother up. The woman saw “blood underneath the door” and told her daughter to call the police, she said.

They waited until they heard the boyfriend close the front door before they came out, she said.

“If I’d have walked out and he was fleeing the scene, I’m a witness so he would have stabbed me too,” the teenager said.

When cops opened her neighbor’s door, Diamond said “It was blood on the walls, blood on the floor like towards the bedroom. It was blood everywhere.”

The 45-year-old maniac who allegedly carried out the bloodbath changed his clothes and fled, authorities said.

The suspect was last seen wearing a neon vest and a hardhat at a construction site at 163rd Street and College Avenue, cops said.

Police said the dispute was domestic in nature.

“I saw the little boy,” the teen said. “He was still conscious but he looked loopy like he was about to pass out.  They took him out in a chair all bloodied. There was blood dripping from his mouth, his neck was bloody down to his clothes to his feet. The face was very, very bloody.”

In the past, she’d heard him telling Hall, “‘I am gonna strangle you’ or like he’d beat her up,” she said.