The horrified mother of a 15-year-old girl viciously slammed to the ground and stomped on by a teenage boy said the horrific caught-on-camera attack followed weeks of harassment — and nearly killed her daughter.

Lucinda Arroyo told The Post that the 14-year-old bully — who has since been jailed on assault charges — goes to school with her daughter and had long been bugging her in a bid for attention, leaving the girl stunned when the harassment turned violent Monday.

“She’s very upset that her whole life has been completely flipped upside down right now,” the devastated mom said — noting her daughter suffered a concussion, bleeding and a potential brain injury during the shocking beatdown on an East Harlem street.

“She was very angry at why he escalated so quickly from one thing to another. This is not even bullying, this is right on assault, and he could have killed her,” Arroyo said.

“I look at her and it’s a miracle that she’s home. I’m always watching her now, I have to watch her.”

Disturbing video spreading on social media showed the masked brute confronting the girl at East 107th Street and Third Avenue around 3:30 p.m. Monday, just after school let out.

The boy is seen blocking her in the crosswalk and threatening to “beat the s–t out of” her as a friend appears to egg him on from behind the camera.

When she tries to go around him, he grabs her from behind, lifts her up and slams her to the pavement, the video shows.

The clip shows the girl lying helpless on the ground as the boy stomps on her head before walking away.

“The video was passed around like entertainment, and that pissed me off the most,” Arroyo said, adding that her daughter woke up in the ambulance after the attack and couldn’t believe what had just unfolded.

“He just ran off and everybody’s just recording, everybody’s just looking at it while this was happening to her,” the distraught mom said.

“He’s gotten in trouble before because it’s a pattern, he’s not going to stop. Until he learns what right and wrong is, obviously he doesn’t know that yet.”

The teen was charged with assault and appeared in court Thursday afternoon, before being remanded into custody.

— Additional reporting by Steven Vago