Investigators believe the argument came to a head Wednesday and got violent when someone threw a pencil at Cedeno, allegedly setting him off, CBS2's Janelle Burrell reported.
At a Wednesday afternoon news conference on Wednesday, Chief Boyce only said that it appeared that the three students had been involved in a dispute that had been ongoing over the first weeks of the school year before it ultimately escalated.
Mayor de Blasio and Schools Chancellor Carmen Farina were on hand to welcome students back into the troubled school less than 24 hours after the stabbing spattered blood across a fifth-floor classroom.
Police say the 18-year-old was taken into custody, but it's not yet clear what prompted the attack.
The Urban Assembly, a nonprofit organization that runs 21 small schools across the city, started the school in 2007. "Abel was a kid who was made fun of in school, they pushed him too far", said one student in tears.
The 15-year-old victim was reportedly stabbed in the chest and was dead on arrival at St. Barnabus Hospital. He has preliminarily been charged with one count of murder, two counts of of attempted murder, one count of manslaughter, one count of attempted manslaughter, two counts of assault, and two counts of criminal possession of a weapon. The NYPD identified the accused as being 16 years old, but sources said he may be 18.
The suspect, armed with a three-inch switchblade, walked out of the the classroom after the stabbing and handed the weapon to a guidance counselor, Boyce said.
The high school is not among the almost 80 New York City schools with metal detectors, officials said.
"The defendant admits to purchasing a (switchblade) knife two weeks before online and stabbing two people", Assistant District Attorney Nancy Borko said. She said fellow students bothered Cedeno in the hall and "talk crap to him".
A chaotic scene unfolded at a Bronx school where a student was killed and a second critically injured in a stabbing on September 27, 2017.
"For the families, we will do all we can to support them and we will do all we can to support the school community which is reeling right now because of this incident".
"I tried to called the school". The school did not have metal detectors before the incident because a prior review deemed that they were not necessary, officials said. She plans to pull her daughters out of school.
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