A white man driven by racial hatred shot dead three Black people in a Florida discount store Saturday before killing himself after a standoff with police, authorities confirmed.

"This shooting was racially motivated, and he hated Black people," Jacksonville Sheriff TK Waters told a news conference about the gunman, who was in his early 20s.

"He targeted a certain group of people and that's Black people. That's what he said he wanted to kill. And that's very clear," Waters added.

According to the sheriff's office, the shooter, who has not yet been identified, entered a Dollar General store wearing a tactical vest, armed with an AR-style rifle and a handgun.

Manifestos discovered by the gunman's family shortly before the attack "detail the shooter's disgusting ideology of hate," Waters indicated, adding that at least one of the guns had hand-drawn swastikas on it.

The shooting took place near Edward Waters University, a historically Black college in the southern US state.

The FBI will investigate the shooting as a hate crime, said Sherri Onks, the bureau's special agent for Jacksonville, a city of nearly one million in the northeast corner of the state.

There was no evidence the shooter was part of a larger group, officials said.

"We know that he acted completely alone," Waters said.

With easy access to firearms in most states, mass shootings have become common across the United States. 

Florida Governor Ron DeSantis, who is vying to be the Republican Party's presidential candidate for 2024, described the shooting as "horrific" and called the gunman a "scumbag".

The shooting was part of a weekend spate of gun violence in the United States.

Earlier Saturday, at least seven people were hospitalized after a shooting at a Caribbean festival in the northeast city of Boston, police said.

Meanwhile, two women were shot at a baseball game in Chicago the night before.

That same night, a 16-year-old was shot dead, and four others were hurt after an argument erupted at a high school football game in Oklahoma, police confirmed.

The White House said US President Joe Biden was briefed on the Jacksonville shooting and had received updates on other shootings over the last 24 hours across the country.

The deadly incident in Jacksonville is the latest in a series of racially motivated shooting sprees in the United States.

In May 2022, a self-declared white supremacist, Payton Gendron, killed 10 Black people in a live-streamed shooting rampage at a supermarket in New York state. Gendron pleaded guilty in state court to the killings in November and was sentenced to life in prison, but still could face the death penalty in a federal case.

In 2015, a white assailant opened fire at nine Black people during a bible study at a church in Charleston, South Carolina. The shooter, Dylann Roof, is currently on death row.

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