NEW YORK (CBSNewYork) — The mother of an autistic teen who disappeared from school and was later found dead warned a teacher that her son was a runner and needed constant supervision, according to a report released Thursday.

And as CBS 2’s Andrea Grymes reported, the case broke the city’s heart – 14-year-old autistic student Avonte Oquendo was seen on surveillance camera running out of his school, and was never seen alive again. Three months later, Avonte’s remains were found along the shoreline in Queens.

The report released Thursday by New York City Schools Special Commissioner of Investigation Richard Condon detailed the series of events that led up to Avonte’s disappearance from the school in October of last year.

The report does not find one person responsible for Avonte leaving his Queens public school. Rather, it detailed a tragic chain of events involving several people.

“It’s terrible,” Condon said. “I mean, so many things could have intervened that would have prevented this from happening.”

Avonte’s mother, Vanessa Fontaine, spoke out Thursday evening after the report was released.

“Someone has to pay for this mistake,” she said.

Avonte was a student at the Riverview School in Queens when he ran out of the building on Oct. 4, 2013.

An intensive search for the missing teen ensued, and his remains were found in the East River offshore from College Point in January.

The report details interviews with numerous adult staffers inside the Riverview School, and puts together a five- to 10-minute time frame leading up to Avonte leaving by himself.

Avonte’s teacher had previously sent the teen home with a form which Fontaine filled out warning that her son might run, according to the report by the Special Commissioner of Investigation for the New York City School District.

Fontaine wrote on the form “Safety concerns – Please make sure you keep an eye out he likes to run. Need 1-1 supervisor will leave the building.”

Click here to read the full report (.pdf)

“I did write down my concerns that my son was a runner, and to please watch him,” Fontaine said.

That form was unofficial, and though the teacher received it, she never shared it with the school’s administration, according to the report.

“And I did write down my concerns that my son was a runner and to please watch him,” Fontaine said to reporters, including WCBS 880’s Peter Haskell.

The teacher also didn’t tell other staffers who were watching students on the day of his disappearance about Avonte’s potential to run away, according to the report.

That day, Condon said Avonte was with 11 other students, a teacher, and two paraprofessionals when he was able to slip away – walking from the fifth-floor cafeteria to a second-floor classroom.

“You have a teacher with some of the children, and a big space, and then a para with some of the children, and a space, and then the other para with some of the children,” Condon said.

The report said a father waiting to pick up his sick child saw Avonte in the lobby, as did a school safety agent assigned there.

“Twice, (school safety agent) Perez called out ‘excuse me’ to the boy, but he did not respond,” the report said. “SSA Perez could not chase after the student because she was the only SSA at the main security desk and could not leave her post.”

The report said Perez had no idea Avonte left the building, although she remembered seeing him enter the stairwell and head upstairs, according to the report.

But one of the paraprofessionals noticed Avonte was missing.

The agent told an assistant principal Avonte hadn’t left the building. That assistant principal then asked the principal in charge of the building to call for a “soft lockdown,” but the principal initially refused due to concern over alarming the students, according to the report.

The principal eventually ordered the lockdown after hearing that the safety agent wasn’t sure if the student she saw went back upstairs or left the building.

Meanwhile, the search for Avonte started, but Condon said by that time, Avonte was outside.

Condon said what surprised him most was that the principal in charge of the building did not have immediate access to surveillance video that captured Avonte leaving.

“If they’d had it, and then they looked at the right camera, they would’ve seen him go out the door, and that just changes the whole focus of the search,” Condon said.

Investigators Thursday were still trying to piece together who left the building door open that Avonte left through.

The Department of Education issued a statement in response to the report.

“The situation was truly tragic. Our school communities mourned. And today, we learned more about what happened on that fateful day,” spokesman Devon Puglia said in the statement “We are reviewing the report closely and are committed to working diligently to prevent another tragedy like this from ever occurring again. Our thoughts are with Avonte’s family.”

The department said it has already taken steps to “enhance and refine existing protocols” so as to keep a similar situation from happening in the future.

The protocols include Building Response Teams, which are stationed in each school building to coordinate teacher, student and staff actions until first responders arrive; mandatory school safety plans; and training for new NYPD School Safety Division recruits.

The family’s attorney David Perecman told 1010 WINS’ Carol D’Auria he wonders why the report doesn’t recommend that anyone be disciplined, specifically singling out Perez.

“Disciplinary action? She’ still working there. No one was reassigned as a result of this investigation,” Perecman said.

After Avonte’s remains were found in January, the New York City Medical Examiner’s office could not determine how he died.

Avonte’s family has filed a lawsuit against the city.

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