About 200 people attended a vigil on Sunday evening near the Dollar General store in Jacksonville where officials said 21-year-old Ryan Palmeter opened fire the day before using guns he had bought legally.

The southern state’s Republican Governor Ron DeSantis – who has weakened Florida’s gun control laws and attacked so-called “wokeness” – was booed loudly as he addressed the vigil.

DeSantis promised financial support for security at Edward Waters University, the historically black college near where the shooting took place, and to help the affected families.

“What he did is totally unacceptable in the state of Florida,” DeSantis said of the killer. “We are not going to let people be targeted based on their race.”

Sheriff TK Waters identified the victims as Angela Michelle Carr, 52, who was shot multiple times in her car; store employee AJ Laguerre, 19, who was killed as he tried to escape; and customer Jerrald Gallion, 29, who was shot as he walked into the shop in a predominantly Black neighbourhood.

Gallion was part of the congregation at St Paul Missionary Baptist Church in Jacksonville.

“In two weeks I have to preach a funeral of a man who should still be alive,” the church’s Bishop John Guns told those assembled for the vigil. “He was not a gangster, he was not a thug — he was a father who gave his life to Jesus and was trying to get it together.”

Biden noted the shooting took place on the same day the country marked the 60th anniversary of the March on Washington, scene of Martin Luther King Jr’s famous “I Have a Dream” speech.

“We must say clearly and forcefully that white supremacy has no place in America,” President Joe Biden said in a statement on Sunday.

“We must refuse to live in a country where Black families going to the store or Black students going to school live in fear of being gunned down because of the colour of their skin.”

The Justice Department is investigating the shooting as a hate crime and an “act of racially motivated violent extremism”, US Attorney General Merrick Garland said in a statement.

Biden spoke to Jacksonville Mayor Donna Deegan and Sheriff Waters in the wake of the shooting. In both calls, he offered his full support to the people of Jacksonville, according to a White House statement.

The latest in a long history of American racist killings unfolded on Saturday afternoon after Palmeter first parked at Edward Waters University.

The sheriff said a video posted on TikTok without a timestamp showed Palmeter donning a bullet-proof vest. A university security guard spotted Palmeter and parked near him. Palmeter drove off and the security guard flagged down a Jacksonville sheriff’s officer who was about to send out an alert to other officers when the attack began.

Covering his face with a mask, Palmeter used a handgun and an AR-15 style rifle, with swastikas on it, police said, referring to a lightweight semiautomatic long gun often used in mass shootings.

The gunman had no criminal record and while he had been involuntarily committed for a mental health examination in 2017, he was then released so it would not have shown up on his background checks, police added.

Right-wing rhetoric blamed

Palmeter lived with his parents in a suburb of Jacksonville. He texted his father during the shooting and told him to break into his room, Waters said. The father then found a suicide note, a will and the racist writings Waters described as “quite frankly, the diary of a madman”.

“He was just completely irrational,” Waters said. “But with irrational thoughts, he knew what he was doing. He was 100 percent lucid.”

The sheriff said Palmeter, wearing his vest covered by a shirt, gloves and a mask, first stopped in front of Carr’s vehicle and fired 11 shots with his rifle through her windscreen, killing her.

He entered the Dollar General store and turned to his right, shooting Laguerre, according to video. Numerous people fled through the back door, the sheriff said. He chased after them and fired, but missed. He went back inside the shop and saw Gallion entering the front door with his girlfriend. He fatally shot Gallion.

He then chased a woman through the store and fired, but missed.

Elected officials said racist attacks like Saturday’s have been encouraged by political rhetoric targeting “wokeness” and policies from the Republican-led state government headed by DeSantis, including one taking aim at the teaching of Black history in Florida.

“We must be clear, it was not just racially motivated, it was racist violence that has been perpetuated by rhetoric and policies designed to attack Black people, period,” said state Representative Angie Nixon, a Jacksonville Democrat.

“We cannot sit idly by as our history is being erased, as our lives are being devalued, as wokeness is being attacked,” Nixon said. “Because let’s be clear — that is red meat to a base of voters.”

Rudolph McKissick, a national board member of the Reverend Al Sharpton’s National Action Network, Baptist bishop, and senior pastor of the Bethel Church in Jacksonville, was in the city on Saturday when the shooting happened.

“Nobody is having honest, candid conversations about the presence of racism,” McKissick said.

Past shootings targeting Black Americans include an attack at a Buffalo supermarket in 2022 and a historic African Methodist Episcopal church in Charleston in 2015.

The Buffalo shooting, which killed 10 people, stands as one of the deadliest targeted attacks on Black people by a lone white gunman in US history. The killer was sentenced to life in prison without the possibility of parole.