BUFFALO, N.Y. (AP) — The white man accused of killing 10 Black people at a supermarket in Buffalo appeared in court Thursday, standing silently during a brief proceeding attended by some relatives of the victims after a grand jury indicted him.

Payton Gendron, 18, wore an orange jail uniform, a mask and handcuffs. As he was led out, someone shouted “Payton, you’re a coward!” from the courtroom gallery. He is being held in jail without bail.

Assistant district attorney Gary Hackbush said the first-degree murder indictment, which covers all 10 deaths, was handed up Wednesday.

Thirteen people in all were shot Saturday at the Tops Friendly Market in a predominantly Black neighborhood of Buffalo. Authorities are continuing to investigate the possibility of hate crime and terrorism charges.

District attorney John Flynn said his office would not comment on the case while the grand jury investigation continues.

Calls seeking comment were made to Gendron’s lawyers.

The victims’ family members who had attended the hearing left without immediately speaking to reporters.

Gendron, 18, livestreamed the attack from a helmet camera before surrendering to police outside the grocery store. Shortly before the attack, he posted hundreds of pages of writings to online discussion groups where he detailed his plans for the assault and his racist motivation.

Investigators have been examining those documents, which included a private diary he kept on the chat platform Discord.

At his initial court appearance last week, Gendron’s court-appointed lawyer entered a plea of “not guilty” on his behalf. He is due back in court June 9.

The massacre at the Tops supermarket was unsettling even in a nation that has become almost numb to mass shootings. All but two of the 13 of the people shot during the attack were Black.