A 15-year-old high school freshman was fatally stabbed during a fight that started when one student bumped another after classes were dismissed Wednesday at a Northeast Washington charter school, according to a D.C. police detective who spoke to the suspect.

The detective, testifying at a juvenile court hearing for the 16-year-old who was charged with second-degree murder while armed and with carrying a dangerous weapon, said the suspect encountered two youths fighting after the bumping incident. The detective said that the victim, Kemon Payne, confronted the suspect and that they fought.

In the midst of the scrum, police said, Kemon, who started classes last week at KIPP DC College Preparatory public charter school, was stabbed twice in the chest. He died at a hospital. He was the third person to be killed in a matter of hours in D.C.

The suspect’s attorney said in court that Kemon and his friends had assaulted her client four times in the past two years, an assertion that the victim’s grandmother, Valerie Payne, later denied.

“We don’t have any answers to what happened,” the 62-year-old Payne said in a telephone interview before the court hearing. She described her grandson in that interview as energetic and loving.

She said the boy’s father had driven to the school to pick up his son, who sent him a text message assuring him he was on his way to the car near the school’s front entrance in the 1400 block of Brentwood Parkway NE.

But Kemon never made it. His grandmother said his father grew worried when he saw a large group form at a bus stop about 3:10 p.m., 15 minutes after students had been dismissed from school on the five-acre campus near Union Market. It was one of the first schools in the city to open last week for the fall semester.

The suspect was charged as a juvenile, meaning that his identity is sealed in court records. The Washington Post generally does not identify teenagers charged with crimes as juveniles. Journalists were allowed to watch the 16-year-old’s hearing via video after agreeing not to report identifying information about him.

After a hearing that lasted more than five hours in the juvenile division of D.C. Superior Court, Magistrate Judge Tyrona T. De Witt denied a request from the suspect’s attorney to throw out the criminal charges or at least release the teen to the custody of his father. She ordered that the suspect remain in secure detention with the city’s Department of Youth Rehabilitation Services during the proceedings.

The defense attorney, public defender Varsha Govindaraju, said her client is “an amazing kid” who has been “an honor roll student his entire life” and wants to be a zoologist. She said he had never been in trouble with the law before Wednesday. Govindaraju also said the victim was bigger than her client and was “a trained boxer” who had been part of a group of teenagers who attacked her client in the past.

Detective Konrad Olszak of the D.C. police, who interviewed the suspect and other witnesses, testified that on Wednesday, a friend of Kemon’s bumped into the 16-year-old in front of the school.

“The kid that bumped him said, ‘Watch out, ‘bro,’ ” Olszak testified. The 16-year-old replied, “What do you mean? You bumped me,” and the other teen said, “What are you going to do about it?”

Olszak said the suspect told him he routinely carried a knife to school, hiding it in bushes behind the building in the mornings and retrieving it on his way home. Olszak said that after the bumping incident, the 16-year-old went behind the school, got his knife out of the bushes and returned to the front of the school. By then, a fight had broken out.

One of the combatants was a friend of the suspect, Olszak said. The other teen in the fight was the friend of Kemon’s who had earlier bumped into the 16-year-old. Olszak said the 16-year-old told him that as he approached the teenagers who were fighting, Kemon stepped in the way.

The suspect quoted Kemon saying, “I wish you would. You know what’s going to happen,” according to Olszak. The two then got in a physical altercation, with the 16-year-old holding a knife.

Olszak testified that the suspect told him that “he put his head down, and the next thing he knew, he looked up and saw [Kemon] bleeding. … Later in the interview, he did say he swung. He just wanted to get [Kemon] off of him. … He said he felt some punches.”

The detective said two witnesses told police the 16-year-old suspect then ran, shouting, “I told you I was going to get you.”

Kemon staggered and cried: “He stabbed me. He stabbed me.”

The knife was found in a grassy area near the school, close to where the 16-year-old was stopped by police as he was running away. A photo of the knife, displayed in court, showed it had a short, wide metal blade, painted sky blue, attached to a long, narrow handle.

KIPP DC spokesman Adam Rupe said the school hires two off-duty police officers each day for dismissal. The officers were on the campus, but authorities are still piecing together where everyone was and what led to the altercation. D.C. police said one officer was inside the school and called for help after noticing a large group of students out front who appeared to be lingering.

Kemon had attended orientation a week earlier, when for the first time nearly all students began in-person learning since schools shut down in March 2020 to contain the spread of the coronavirus. Kemon had been with KIPP DC since preschool, attending school at the network’s campus on Douglass Road SE, closer to his home.

Payne, the victim’s maternal grandmother, described Kemon as an energetic, caring teenager who boxed in his spare time and had recently won a trophy at his first boxing tournament in Philadelphia.

“He was caring,” Payne said, adding that her grandson was big for his age but was always peaceful. “He wanted to protect his family from everything.”