A man accused of killing 22 people at a Walmart in El Paso, Texas, last year, where he was targeting victims of Hispanic origin, has been charged with 90 counts of federal hate crimes.
Patrick Crusius, 21, already faces capital murder charges in state court.
He could face the death penalty under the new charges if found guilty of the attack in August 2019.
A prosecutor said the shooting was an act of domestic terrorism and an attack against an entire ethnic group.
What happened in El Paso?
The shooting, believed to be the eighth deadliest in modern US history, took place in a border city of 680,000 residents that is 80% Hispanic.
Crusius is accused of driving 11 hours to El Paso from his hometown of Allen, near Dallas, on 3 August and opening fire with an AK-47 style rifle inside the Walmart store.
He then surrendered and confessed that he was targeting Mexicans.
In a manifesto posted on the now-defunct message board 8-chan, he wrote that the killings were "a response to the Hispanic invasion of Texas".
Crusius faces the death penalty on a state capital murder charge, to which he pleaded not guilty last year.
What are the latest charges?
The new federal charges include 22 counts under the US classification of hate crimes - violence with an added element of bias - resulting in death. This could also result in the death penalty.
"We're firing on all cylinders to stop this. We're going to stop hate crimes," John Bash, the attorney for the western district of Texas, told reporters.
The indictment references Crusius's manifesto, where he stated he was defending the US "from cultural and ethnic replacement brought on by the invasion".