A white man armed with a high-powered rifle and a handgun killed three Black people at a Dollar General store in Jacksonville, Florida, on Saturday, before shooting himself, in what local law enforcement described as a racially motivated crime.

"This shooting was racially motivated, and he hated Black people," Jacksonville Sheriff T.K. Waters told a press conference.

The suspect, whom Waters described as a white male wearing a tactical vest, was not identified. Waters said all three victims - two men and a woman - were Black.

Waters said authorities believed the shooter acted alone, and that before the shooting he had authored "several manifestos" for media, his parents and law enforcement detailing his hatred for Black people.

Waters described his weapons as a Glock and an "AR-15 style" rifle, with swastikas on it, referring to a lightweight semi-automatic long gun often used in mass shootings.

"The hate that motivated the shooter's killing spree adds an additional layer of heartbreak," Waters said.

He said the shooter was spotted at a local historically Black college, Edward Waters University, where he put on his vest and a mask before going to the local branch of the Dollar General, a discount chain with stores across the United States.

Sherri Onks, special agent in charge of the Jacksonville FBI office, said federal officials had opened a civil rights investigation and would pursue the incident as a hate crime.

"Hate crimes are always and will always remain a top priority for the FBI because they are not only an attack on a victim, they're also meant to threaten and intimidate an entire community," Onks said.

U.S. President Joe Biden and Attorney General Merrick Garland were briefed on the incident.

Mass shootings have become commonplace in the U.S., with more than 469 so far in 2023, according to the Gun Violence Archive.

The nonprofit group defines a mass shooting as any in which four or more people are wounded or killed, not including the shooter.

Saturday's incident in Jacksonville bears similarity to last year's shooting in Buffalo, where a white supremacist killed 10 Black people, and took place five years after another gunman opened fire during a video game tournament in Jacksonville, killing two people before shooting himself.

Florida Governor Ron DeSantis condemned the shooting and said the shooter took "the coward's way out".

"The shooting, based on the manifesto that they discovered from the scumbag who did this, was racially motivated. He was targeting people based on their race. That is totally unacceptable," DeSantis said.