Jacksonville, Florida - A white man driven by racial hatred shot dead three Black people in a Florida discount store Saturday before taking his own life after a standoff with police, authorities said.

"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," Jacksonville Sheriff TK Waters told a news conference about the gunman, who was in his early 20s.

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 said, and at least one of the guns had hand-drawn swastikas on it.

The shooting took place near Edward Waters University, a historically Black college. The university said in a statement that the shooter had been on campus earlier that day, though no one was harmed.

"An on-campus Edward Waters University security officer engaged an unidentified male in the vicinity of the Centennial Library on campus," it said. "The individual refused to identify themselves and was asked to leave."

The university added that the individual – later identified as the shooter – left "without incident."

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.

Mass shootings have become disturbingly common across the United States, with easy access to firearms in most states and more guns in the country than citizens.

Florida Governor Ron DeSantis decried the "horrific" shooting and called the gunman a "scumbag."

"He was targeting people based on their race, that is totally unacceptable," said DeSantis, who is vying to be the Republican Party's presidential candidate for 2024. "This guy killed himself rather than face the music and accept responsibility for his actions and so he took the coward's way out."

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 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 hurt after an argument erupted at a high school football game in Oklahoma, police said.

US President Joe Biden was briefed on the incident in Jacksonville, the White House said, 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 racist 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, who targeted the store because of the large African-American population in the area, 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 gunned down nine Black people during a Bible study at a church in Charleston, South Carolina. The shooter, Dylann Roof, is currently on death row.

Saturday's shooting in Jacksonville came five years to the day after another mass shooting in the city when a gunman at a video game tournament killed two and wounded several others before killing himself.