The boy who died, Matthew McCree, was stabbed in the chest, according to the police. He was taken to St. Barnabas Hospital, where he was pronounced dead. The other victim was stabbed in the arm and the torso, and was in critical but stable condition. The other victim’s name had not been released.

In an interview, Kevin Sampson, a dean at school, said the fatal confrontation stemmed from “bullying,” and at a news conference on Wednesday afternoon Chief Boyce said it appeared the three students had been locked in a running dispute over the first weeks of the school year, and that it blew up inside a fifth-floor history classroom around 10:45 a.m. in front of about 20 other students.

The stabbings — and the presence of a switchblade in the school — stirred complaints from some parents that the school did not have metal detectors and prompted questions from reporters to the mayor and police officials about whether the school should have had them. Eighty-eight of the city’s roughly 1,300 school buildings have metal detectors that are used either full time or part time.

Among students and faculty, though, the talk was of the lives changed.

Shortly after they were released from the lockdown on Wednesday afternoon, Asia Johnson and Yanique Heatley, both 18, stood outside the high school at 2040 Mohegan Avenue in the West Farms neighborhood.