A crime scene cleaning service discovered the black folding knife on the fifth floor of the Urban Assembly School for Wildlife Conservation at 2024 Mohegan Ave. on Sept. 28 when detectives reopened the classroom after the investigation, according to police and union officials.
"It was outside the crime scene, the immediate crime scene, where we recovered it in the same classroom," NYPD Chief of Detectives Robert Boyce said.
The blade belonged to a 16-year-old boy who was in the classroom at the time of the attack, but was not linked to the fight that left Matthew McCree, 15, dead and Ariane Laboy, 16, critically wounded in the attack by Abel Cedeno, 18.
"We spoke to the person who had the knife," Boyce said. "The kid had nothing to do with the stabbing at all. Neither did the knife."
The chief added that the teen had the knife in his backpack at the time of the attack.
"He knocked it over, and several items in the backpack fell out," Boyce said. "He didn't secret this. I take him at his word. It was well on the other side of the room."
The stabbings came after Laboy and McCree started throwing pencils and wads of paper at Cedeno, who a family spokeswoman said had been bullied for weeks.
The school had not previously contained metal detectors, but authorities beefed up security and added the scanners along with more safety officers in response to the attack.
Gregory Floyd, president of the school safety officers union, Teamsters Local 237, had previously called for metal detectors and increased security at the school.
"How many other students had weapons that we didn't know about?" he said.
McCree's mother, Louna Dennis, said Tuesday she was "not surprised" by the fact that there was a second weapon in the classroom and expressed anger over the way the school's administration handled safety and discipline.
Her family's lawyer, Sanford Rubenstein, agreed.
“Certainly the second knife demonstrates the fact that there’s a serious problem with weapons in classrooms in the public school system in this city and there should have been metal detectors at this school before this young man was killed," Rubenstein said while standing with Dennis outside the Bronx courthouse Tuesday morning.
The city Department of Education referred calls for comment to the police department.