BUFFALO, N.Y. — The white gunman charged with killing 10 Black people in a racist mass shooting at a Buffalo supermarket pleaded not guilty Monday to federal hate crime charges that could be punishable by the death penalty.

Payton Gendron was indicted last week on hate crimes and weapons counts. The plea was entered in court by Gendron’s attorney, who said she hoped to resolve the case before trial. Wearing an orange jumpsuit and shackles, Gendron was silent during the brief arraignment.

The 27-count federal indictment contains special findings, including that Gendron engaged in substantial planning to commit an act of terrorism and took aim at vulnerable older people — specifically 86-year-old Ruth Whitfield, 77-year-old Pearl Young, 72-year-old Katherine Massey, 67-year-old Heyward Patterson and 65-year-old Celestine Chaney.

The Justice Department said a decision on whether to seek the death penalty against the shooter, who turned 19 in June, would come later.

Gendron, who livestreamed the May 14 attack, was arrested just outside the entrance of the Tops Friendly Supermarket after donning body armor and opening fire on weekend shoppers and employees in the parking lot and inside. Three people were wounded.

The store reopened to the public last week, two months after the attack.

Investigators say the shooter drove for more than three hours from his home in Conklin, New York, to a busy grocery store chosen for its location in a predominantly Black neighborhood, with the intent of killing as many Black people as possible. He was motivated, they said, by white supremacist beliefs which he described in online diary entries.

Gendron wrote as far back as November about staging a livestreamed attack, practiced shooting from his car and did reconnaissance on the store two months before carrying out the plans, according to the writings.

He arrived at the store wearing camouflage clothing and a tactical-style helmet fitted with a video camera.

The indictment seeks the forfeiture of an extensive arsenal recovered from Gendron’s car and home. It includes the Bushmaster XM-15 semi-automatic rifle used in the shooting and a 12-gauge loaded shotgun and loaded bolt-action rifle and ammunition taken from the car. Authorities seized additional ammunition and firearms accessories from his home.

The federal indictment charges Gendron with 10 counts of hate crimes resulting in death, three counts of hate crimes involving an attempt to kill three people and another hate crime count alleging Gendron tried to kill other Black people in and around the store. It also includes 13 counts of using a firearm in a hate crime.

Gendron also faces a parallel state prosecution on charges including hate-motivated domestic terrorism, murder and attempted murder as a hate crime. The domestic terrorism hate crime charge carries an automatic life sentence. He has pleaded not guilty to those charges as well.