Abel Cedeno was sentenced to 14 years in prison this week for stabbing one classmate to death and wounding another at the Urban Assembly School for Wildlife Conservation in the Bronx.

A report by the Special Commissioner for Investigation now says an assistant principal had been warned three years before the killing that Cedeno was carrying a knife to school, but failed to take proper action.

"I'm lost for words to be honest with you, because all of this could have been prevented,” said Louna Dennis, the mother of the child who died. “All this could have been prevented, and I would have had my son with me.”

The report, which only refers to Cedeno as “Student A,” says his mother left a voicemail with a teacher in May of 2014, warning that she found a knife in his backpack.

The report says the teacher immediately notified Assistant Principal Caridad Caro.

"The voicemail was out of concern for our students and staff safety because he has a history of pulling knives on his family,” wrote the teacher. “This is an issue that needs to be addressed immediately.”

But the report says Caro failed to enter the incident in the DOE's online reporting system.

She told investigators she searched the student's backpack instead, although only school safety agents are supposed to conduct such searches.

She said she found no knife, so took no further action.

“Three and a half years later, in September 2017, Cedeno used another knife to kill Matthew McCree and wound another student, Ariane Laboy,” said Louna Dennis.

He claimed he took the knife to school after being bullied because he is gay.

But the judge who presided over the non-jury trial rejected Cedeno's claim that he acted in self-defense.

And the report by the Special Commissioner for Investigation said it found no evidence Cedeno ever reported any bullying.

The school was closed in 2018, and Caro was sent to an office in Brooklyn, where she continues to work.

McCree's family is suing the city for millions of dollars in damages.