Teen charged with murder for stabbing fellow student to death with switchblade.

The taunting began on the first day of high school and continued until Abel Cedeno couldn’t hold his rage another second.

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The bullied student, armed with a $30 switchblade, stabbed one of his tormentors to death and savagely gashed a second teen as a Wednesday morning history class turned into a Bronx bloodbath, police said.

Horrified classmates howled in disbelief as Cedeno flew into a homicidal fury, plunging the serrated stainless steel blade into the chests of Matthew McCree, 15, and Ariane Laboy, 16.

The knife-wielding Cedeno just “went crazy,” said witness Jomarlyn Colon, 16. “Everybody just stood back. A few of them were holding Matthew. A few of them were holding towels on the wound. “All the kids were crying and screaming.”

McCree, who started the deadly confrontation by flicking a pencil at Cedeno, was pronounced dead at St. Barnabas Hospital after the 10:50 a.m. stabbing spree in a fifth-floor classroom, cops said.

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Laboy was in critical condition at the same hospital after he was slashed while coming to McCree’s defense.

Cedeno was charged with murder, attempted murder, manslaughter, attempted manslaughter, assault and criminal possession of a weapon.

As cops escorted him out of the 48th Precinct Wednesday night, he mouthed “yes” when reporters asked if he had been bullied.

The killing at the Urban Assembly School for Wildlife Conservation was the first inside a city school since February 1993.

The school is not equipped with metal detectors that could have alerted authorities to the knife, said sources with knowledge of the incident.

Colon said students were unable to hold the enraged Cedeno back as the 18-year-old student yanked the knife — reportedly purchased via Amazon — from his top shirt pocket.

A source indicated the recovered blade was “very illegal” and not for sale in New York State.

Cedeno told detectives that the two stabbed teens were “harassing him for awhile,” and sources said the bullying of the typically low-key victim began when schools opened on Sept. 7.

“He’s a good kid,” said Norma Perez, 69, a surrogate grandmother for the teen. “I don’t know what happened this morning. I just know he’s not like that.”

The third-period history class was about 30 minutes old when Cedeno stood up to leave the room — and McCree tossed his pencil at the older boy, cops said.

Though the projectile missed Cedeno, he turned to face McCree. The younger student immediately stepped up to confront him, setting off the violent attack, cops said.

Source: nydailynews.com