The Thursday hearing before Buffalo City Court Judge Craig Hannah had prosecutors state in court that a grand jury investigating the case had voted to indict the suspect, Payton Gendron. He was ordered to remain in custody without bail.
Erie County, New York District Attorney John Flynn said Gendron remains charged with a single count of first-degree murder in a criminal complaint presented during an arraignment hours after the shooting of 13 people - 11 of them Black - at a Tops Friendly Markets store on Saturday afternoon. Ten of the victims died.
Gendron faces life in prison without parole if convicted on the murder charge.
Flynn said in his statement he would have no further comment on the case until the grand jury's work was done.
As Gendron was escorted into the courtroom in shackles on Thursday wearing orange jail garb and with a white medical mask over his face, someone in the courtroom gallery shouted, “Hey, you’re a coward!”
The rampage, which authorities said the accused gunman had carefully planned with an eye toward killing as many Black people as he could, has touched a nerve in a country that has grown accustomed to mass shootings.
Authorities said the suspect broadcast video of the attack to a social media platform in real time after posting white supremacist material online showing he had drawn inspiration from previous racially motivated mass killings.
The circumstances of the Buffalo attack have revived a national debate about guns, domestic terrorism, hate and the internet's role in spreading it.
The FBI has said the shooting is under investigation as a hate crime and an act of "racially motivated violent extremism."