The teenage gunman accused of shooting 10 people dead in a supermarket in Buffalo, New York, last month has been charged with domestic terrorism.
Prosecutors allege 18-year-old Payton Gendron, who earlier pleaded not guilty, was motivated by racial hatred.
The suspect, who describes himself as a white supremacist, is accused of shooting 13 people in total during the massacre - almost all of them black.
He will also face 10 separate first-degree murder charges.
The domestic terrorism charge filed on Wednesday accuses the suspect of killing "because of the perceived race and/or colour" of his victims.
In addition, the 25-count indictment includes multiple murder charges and attempted murder as hate crimes, as well as weapon possession charges, news agency AFP reports.
Ten people were killed and three injured in the May 14 shooting, when the suspect is accused of having driven more than 320km (200 miles) to a predominantly black neighbourhood in Buffalo, New York's second-largest city.
After the attack, Mayor Byron Brown said the suspect had travelled there with the specific intention of ending "as many black lives as possible".
An 180-page document seemingly authored by the alleged attacker has since emerged, in which he describes himself as a fascist and a white supremacist.
The gunman, dressed in military gear, drove into the car park at the city's Tops Friendly Market and began livestreaming the shooting spree.
A security guard fired several shots at the attacker, but police said he was protected by a bulletproof vest. The gunman is accused of killing the guard before continuing his attack.
All of the 10 people who were killed were black.
Among those shot dead, who ranged in age from 32 to 86, were a man buying cupcakes for his son's birthday and a woman who had gone shopping after visiting her husband at a nursing home.
Separately, New York state's top prosecutor is investigating whether social media companies enabled the attack by allowing it to be streamed, promoted, or planned over their platforms.
"The fact that an individual can post detailed plans to commit such an act of hate without consequence, and then stream it for the world to see is bone-chilling and unfathomable," Attorney General Letitia James said.
Twitch, the website where the attack was streamed, said the video was taken down less than two minutes after the violence began - but not before it was duplicated and shared on other streaming sites.
The United States is currently experiencing an epidemic of gun-related violence, with data from the CDC suggesting that 54 people are killed each day by a firearm.
Just 10 days after the attack in Buffalo, a different 18-year-old gunman wielding the same AR-15 style assault rifle stormed a primary school in Uvalde, Texas, killing 19 children and two adults.
Speaking after the Uvalde attack, US President Joe Biden called on American lawmakers to pass "common-sense" gun laws.
"What in God's name do you need an assault weapon for except to kill someone?" he asked. "We have to make it clear to every elected official in this country: It's time to act."
Democratic politicians are pushing for tighter restrictions on firearms and are currently weighing up what national reforms to put to Congress - including bans on certain types of weapons or further restrictions on who can buy guns.
According to US politics website The Hill, House of Representatives Speaker Nancy Pelosi said on Wednesday that an assault weapon ban was being considered too.
But given how few Republicans lawmakers are open to new gun legislation it will be a long shot for Senate Democrats to get the 60 votes they effectively need to turn an assault weapons ban into law.