The judge issued a stern warning to the public in the courtroom and at least three people were removed from the courthouse in the trial that has drawn national attention.

McKINNEY, Texas — Witnesses called by the prosecution in the fatal stabbing of a student at a track meet testified Friday that Karmelo Anthony provoked the altercation that led to the death of 17-year-old Austin Metcalf, a student from a rival high school, as testimony continued in a Texas murder trial.

After a tense start that resulted in the removal of several members of the public from the courthouse, classmates of Metcalf took the stand. They testified that Anthony had sat uninvited in the bleachers under the tent reserved for Metcalf’s school, Memorial High School in Frisco, Texas. Anthony attended crosstown rival Centennial High School.

Multiple witnesses testified that Metcalf had confronted Anthony about being in the tent and at one point pushed him, but they maintained that Anthony bore primary responsibility. It was raining that day, according to witnesses and video and photos.

The defense, which has claimed Anthony acted in self defense, sought to establish that Metcalf was the intigator who led efforts to make Anthony leave the tent. Under questioning by defense attorney Toby Shook, one witness agreed Metcalf was bigger than Anthony by some 50 pounds that some people could find him to be intimidating.

Before the classmates testified, state district court Judge John Roach Jr. issued an order barring public identification of any minor witnesses.

The case has drawn national attention, due in part to its racial dynamics. The composition of the jury — which includes no Black members — has drawn criticism from some advocacy groups and trial observers.

Anthony, now 19 and Black, is charged with fatally stabbing Metcalf who was white, in the chest. Anthony was 17 at the time of the killing; under Texas law, 17-year-olds are tried as adults. He has pleaded not guilty. If convicted of first-degree murder, he faces a sentence of five to 99 years in prison.

One 17-year-old witness who said he is entering his senior year, testified Anthony entered the Memorial tent wearing Centennial gear and people began confronting him, telling him he “probably shouldn’t be there. You need to leave our tent.” A couple of witnesses told the court that Anthony seemed to know someone else at the tent.

The witness said he joined in telling Anthony to leave, along with “numerous” members of the football team. Metcalf was a member of the football team and had been an MVP, according to his father. The witness was permitted to hold a football while testifying because, prosecutors said, he likes to have something in his hands when nervous.

Anthony began repeating “touch me and find out” as the two argued, the witness said. Anthony put his hands in his backpack, but his threat wasn’t taken seriously, he said. Metcalf leaned in to push Anthony and was stabbed, the witness added, noting he did not see the knife. Metcalf fell down the bleachers onto his back, then pulled himself up, lifted his shirt, and on seeing his bloodied chest, looked frightened, he testified.

In a courtroom demonstration, defense attorney Shook took on the role of Anthony — seated — while the witness stood over him and pushed him at the shoulders, acting as Metcalf. A later witness recreating the same push used only one hand. Another witness also testified that Metcalf was the only person standing at the time.

Jaylen Matthewes, 18, whose mother is a pediatrician for the Metcalf family, said Metcalf’s push was enough to get Anthony out of his seat but not enough to hurt him. Witnesses agreed that Anthony seemed friendly and relaxed when he first sat down.

Anthony was permitted to graduate from high school and finished with a 3.7 GPA, the civil rights organization Next Generation Action Network told NBC Dallas-Fort Worth.

Track Meet Student KilledSupporters for Karmelo Anthony demonstrate in front of the Collin County courthouse Thursday in McKinney, Texas.Tony Gutierrez / AP

Before the lunch break, state prosecutor Bill Wirskye showed jurors a four-minute video of Anthony’s arrest, part of which was captured on the body camera of Officer Eduardo Cortez, a school resource officer with the Frisco Police Department. In the footage, Anthony is seen holding his hands above his head while Cortez radios that he has located the “alleged suspect.”

Anthony, barely audible in the clip, makes a pleading remark. Cortez had testified minutes before that Anthony had said, “I’m not alleged. I did it,” adding: “He put his hands on me. I told him not to. He put his hands on me.”

Anthony’s demeanor at the time became a point of contention — specifically, whether he was crying or calm. Cortez testified that he had described Anthony as emotional in his report, but that characterization applied only to the moment Anthony stated he warned Metcalf not to touch him. A second officer joined them, and the two escorted Anthony to a patrol car. “When we placed him in the squad car, he asked if he was going to be okay,” Cortez said. “I told him I didn’t know.”

Prosecutors also showed jurors photos of the knife recovered at the scene. Wirskye then produced the actual knife — black-bladed — from a white box, wearing black latex gloves. An officer testified it was found three to four rows up from where the stabbing occurred and was not fully open. A replica, also not fully open, was shown to jurors as well. Officer Jacob Shalz of the Frisco Police Department testified that the type of knife is commonly carried as a tool rather than a weapon.

Defense attorney Mike Howard established through questioning that having such a knife would result only in school discipline within the Frisco school district and that possession of a knife with a blade under 5.5 inches is not a crime in Texas. Photos showed the blade measured approximately 3.5 inches.

Prosecutors sought to contrast the composure Anthony displayed at his arrest with the frantic scene at the stadium. Body camera footage showed a bloodied Metcalf on the ground at the base of the bleachers, his twin brother Hunter beside him, wailing.

“My brother, my best friend — hurry up,” Hunter yelled to an officer vaulting a chain-link fence. “He’s very messed up.” A CPR machine could be heard repeatedly saying “press, press, press” as paramedics worked on Metcalf. Audible sobbing came from the gallery as the video played; Metcalf’s family kept their heads bowed.

“We kept doing everything we could,” said Frisco Fire Department paramedic and firefighter Neil Adams, who testified at the start of the day’s proceedings. “It didn’t help.”

Maria Guerrero and Meredith Yeomans reported from McKinney, Texas and Suzanne Gamboa from Austin, Texas.