NEW YORK (CBSNewYork) – A Bronx teenager accused of stabbing a classmate to death and wounding another took the stand Thursday to tell his side of the story.

Abel Cedeno testified that he had been bullied for years and fought back in self-defense, but prosecutors say he had a choice.

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His attorney says he was acting in self-defense after being bullied because of his sexuality.

Cedeno said on the day in September 2017 that he fatally stabbed 15-year-old Matthew McCree and critically injured Ariane Laboy at the Urban Assembly School for Wildlife Conservation, he was punched in the face multiple times.

“I began getting hit in the back of the head with broken pencils, pen caps and bunched up paper,” said Cedeno. “Matthew punched me on the cheek two or three times.”

Cedeno said he tried to defend himself by showing the knife.

“The knife was only meant to scare people away,” he said.

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Prosecutors cross-examined Cedeno, asking if he remembered stabbing McCree and Laboy.

“Not specifically, the times when the blade went inside them,” he said.

“What I don’t understand is, he don’t remember at no point in time he used the knife, but when it comes to the other side he remember everything,” said Luna Dennis, the mother of Matthew McCree. “When it was his turn, he can’t remember anything.

“None of these boys was bullied, they was doing what they did,” she said. “Love life lived. None of these kids was troubled kids.”

“Clearly the attempt to call Matthew a bully is an attempt to dirty up the victim and we won’t stand for it,” said Sanford Rubenstein, the McCrees’ Family attorney.

Cedeno pleaded not guilty to manslaughter, assault and criminal possession of a weapon charges.

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If convicted, he faces up to 25 years in prison.