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WEST FARMS, Bronx — A student who was stabbed to death in his Bronx classroom, and second who was critically injured, bullied their attacker moments before the deadly altercation but did not continuously harass him as previously believed, police said Thursday.

Abel Cedeno was taken into custody after he allegedly stabbed two of his classmates in the Bronx

Abel Cedeno, 18, lashed out with a pocketknife during a third-period history class at Urban Assembly School for Wildlife Conservation on Wednesday, according to police.

Matthew McCree, 15, was fatally stabbed, and a 16-year-old was critically injured in the attack, police said.

The two victims threw pencils and papers at Cedeno, apparently prompting him to engage them in an altercation that ended with him stabbing them both in the chest with a 3-inch switchblade, according to NYPD Chief Robert Boyce.

An ongoing argument between the victims and suspect was initially believed to have lasted two weeks, since school first began, Boyce said Wednesday.

This was in fact Cedeno’s first known time having a problem with these two individuals, Boyce said at a news briefing Thursday.

“He had problems before, at the start of school, but not with these two individuals,” Boyce said.

Cedeno has not specified to investigators what he was bullied about, Boyce said, refusing to speculate when pushed by reporters.

He is also not believed to have told school officials about the bullying, according to Boyce.

Matthew McCree, 15, to was stabbed to death in a Bronx school on Sept. 27, 2017. (Facebook)

The teen has been charged with murder, two counts of attempted murder, manslaughter, two counts of attempted manslaughter, two counts of assault, two counts of criminal possession of a weapon.

After the attack, which happened in front of 15 to 20 other students, officials said Cedeno handed the knife to a school counselor and willingly went to a school office, where he waited for police.

Cedeno allegedly told investigators he bought the switchblade online about two weeks ago “just to possess a knife,” Boyce said of the teen’s comments.

The teen’s mother is in Puerto Rico, likely trapped because of devastation caused by Hurricane Maria, so police have been interviewing his older brother, a man in his 20s, Boyce said.