A white man fatally shot three people inside a Jacksonville, Florida, Dollar General store on Saturday in a predominately Black neighbourhood in an attack that the local sheriff called "racially motivated." The shooter then killed himself.

"He hated black people," Sheriff T K Waters told a news conference. "There is absolutely no evidence the shooter is part of any larger group."

Waters said the shooter, who was in his 20s, used a Glock handgun and an AR-15 semi-automatic rifle with at least one of the firearms painted with a swastika.

He left behind writings that led investigators to believe that he committed the shooting because it was the fifth anniversary of when another gunman opened fire during a video game tournament in Jacksonville, killing two people before fatally shooting himself.

The shooting happened just before 2 pm at a Dollar General near Edward Waters University, a small historically Black university.

The shooter had driven there from neighbouring Clay County. Shortly before the attack, the shooter had sent his father a text message telling him to check his computer. The father found writings and the family notified 911, but the shooting had already begun, Sheriff Waters said.

Edward Waters University students were being kept in their dorms, the school said in a statement. No students or faculty are believed involved, the school said.

Penny Jones told the The Associated Press that she worked at the store until a few months ago. She lives a few blocks away in the predominantly Black neighbourhood.

"I'm just waiting to hear about my co-workers that I used to work with," Jones said. "I don't know if it's safe to move about the neighbourhood."

Jones added that she was "feeling awkward, scared."

"I don't want to leave my house. I'm thinking, do I want to go back to the store? Is this going to start happening more frequently? I don't know what the cause of it is. I'm confused. It's a lot of different feelings going on right now," she said Saturday afternoon.

The deadly shooting took place within hours of the conclusion of a commemorative March on Washington in the nation's capital, where organizers drew attention to the growing threat of hate-motivated violence against people of color.

An attack on a shopping centre in a predominately Black neighbourhood will undoubtedly evoke fears of past shootings targeting Black Americans, like the one at a Buffalo, New York, supermarket in 2022, and one at a historic African Methodist Episcopal church in Charleston, South Carolina, in 2015.

The Buffalo supermarket shooting, in particular, stands apart as one of the deadliest targeted attacks on Black people by a white lone gunman in US history. Ten people were killed by the gunman, who has been sentenced to life in prison without the possibility of parole