(CBS) — A 15-year-old boy accused of a brutal sexual assault on the CTA’s Blue Line train allegedly took $2,000 from the victim and used it to pay for his graduation fees, junk food and Air Jordan track suits, the Chicago Sun-Times is reporting.

Deshawn Isabelle dragged the 41-year-old woman by her long hair, punched her repeatedly and sat on her head during Monday’s attack, Cook County prosecutors said Thursday.

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As of Wednesday, the victim, who suffered concussions and cuts all over her body, was still vomiting as a result of her injuries, Assistant State’s Attorney Joe DiBella said.

Isabelle, who was charged as an adult, was captured on surveillance cameras during the incident and investigators were able to match his fingerprint to those found on a train window he was seen touching and kicking prior to the rape, DiBella said.

The middle school student had gotten on the Blue Line train at the Forest Park stop and was seen wandering around inside around 3 p.m., DiBella said.

When the victim hopped on at the Oak Park stop and sat two seats in front of Isabelle, Isabelle got up and attacked her from behind, punching and dragging her to the ground, DiBella said.

The woman landed on her face and went into a fetal position, covering herself from the punches Isabelle threw before he thrust against her, placed his hands inside her pants and sexually assaulted her, DiBella said.

Isabelle also allegedly groped the woman over her clothing and slapped her buttocks.

He then sat on the victim’s head, restricting her breathing, DiBella said.

Isabelle kept punching the woman and kept her from leaving the train when it stopped by pressing his knees down on her, DiBella said.

No one entered the train, so Isabelle grabbed the woman’s by the hair again and dragged her to a partially enclosed area in the train car where he pushed her face down, DiBella said.

The teenage boy then allegedly kept punching, kicking and stomping all over the woman’s body and demanding cash.

Isabelle eventually took money from the woman’s purse and picked her iPhone off the ground, DiBella said.

He told the woman not to move and remain quiet before he got off the train at the Cicero stop, DiBella said.

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The woman stood up once Isabelle left, but Isabelle put his head back in the train and warned her again to stay put and keep her mouth shut, DiBella said.

When the doors closed and train started to move again, the woman pulled the emergency button and was helped by CTA personnel.

Isabelle told authorities he got on the next train going in the opposite direction and got off the Austin stop, DiBella said.

The teen allegedly threw the victim’s cellphone in a puddle and spent her $2,000, giving some of it away to friends, prosecutors said.

Isabelle’s mother saw his picture on the CTA bulletin and confronted her son, Di Bella said.

She then accompanied him to the Maywood Police station where Isabelle turned himself in Wednesday.

He allegedly wrote a handwritten confession and gave Chicago Police a videotaped statement about his involvement in the assault.

He also took police to where he threw the woman’s iPhone, DiBella said. The phone was recovered and police also retrieved the jacket he wore during the assault and the clothes he purchased with the victim’s money.

Even though Isabelle’s mother helped with turning him in, she was visibly upset when DiBella spoke to the media after the teen’s bond hearing Thursday.

“Quit talking about that s— about my child,” she screamed.

At one point, she saddled up to DiBella with a baby in her lap while the prosecutor stood before TV cameras.

Judge James Brown ordered Isabelle held in lieu of $1 million bail for aggravated criminal sexual assault and robbery.

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(Source: Sun-Times Media Wire © Chicago Sun-Times 2015. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)