But to many, what was more shocking was that the police were seeking three middle schoolers in the attack.

Days after Ms. Majors’s death, a 13-year-old was arrested in the episode — a cellphone robbery gone wrong, according to the authorities.

But months later, two other teenagers remained at large.

That changed this past week, when two 14-year-olds — both classmates of the 13-year-old — were charged with murder.

The latest breaks in the case

The police arrested Rashaun Weaver, 14, on Saturday, charging him in Criminal Court in Manhattan with second-degree murder and robbery. Investigators had long believed that he wielded the knife that killed Ms. Majors as she walked in Morningside Park after dark on Dec. 11.