The 18-year-old white man who killed 10 people at a Buffalo supermarket in a predominantly Black neighborhood on Saturday was motivated by racism and will be prosecuted for hate crimes, authorities said Sunday.

At an afternoon briefing, federal, state and local officials laid out the latest in the investigation into the mass shooting at a Tops supermarket in the state’s second-largest city. And while much remains unknown, the officials made clear the alleged shooter was motivated by hatred and will soon be facing additional charges – perhaps on the federal level.

"The evidence we have uncovered so far makes no mistake that this is an absolute racist hate crime,” said Buffalo Police Commissioner Joseph Gramaglia. “It will be prosecuted as a hate crime. This is someone who has hate in their heart, soul and mind."

Here’s what we know so far

Authorities said 10 people were killed and three others were wounded by the shooter, who drove up to the supermarket and began shooting people in the parking lot before making his way inside. Of the victims, 11 of the 13 were Black.

The alleged shooter, Payton Gendron, was accused of driving three hours from his home in the town of Conklin, just east of Binghamton near the Pennsylvania line, to perpetrate the attack. He broadcast his actions to Twitch, the online streaming platform, via a camera attached to his helmet, officials said.

He was wearing tactical gear, including body armor, which protected him when he was struck by gunfire from Aaron Salter, a former police officer who was working as an armed security guard in the Tops store, according to police. Salter was ultimately shot and killed.

“This individual came here with the expressed purpose of taking as many Black lives as he possibly could,” Buffalo Mayor Byron Brown said.

What we know about the victims of Saturday's attack

Buffalo Police released the names of the victims on Sunday night. They ranged in age from 31 to 86, officials said. Among the dead, the Buffalo News reported, were security guard Aaron Salter, a retired Buffalo police officer who attempted to stop the gunman; Pearl Young, who'd run a food pantry for more than two decades; Ruth Whitfield, the mother of Buffalo's former fire commissioner; civil rights activist Katherine Massey, Heyward Patterson, who helped drive shoppers to and from the supermarket; and Celestine Chaney, a grandmother to six. Geraldine Talley, 62, Andre Mackniel, 53, Margus Morrison, 52 and Roberta Drury, 31, were also killed, according to The Buffalo News. Three others were wounded in the attack.

Police aren’t confirming document's authenticity, but it matches up

During Sunday’s briefing, the Buffalo police commissioner declined to publicly confirm the authenticity of an 180-page document circulating online that purports to be written by the Buffalo shooter.

But the document’s many details – from the name and age of the alleged shooter, to the racist motive cited by police and public officials – matched up. And Gov. Kathy Hochul repeatedly mentioned the manifesto in a number of media interviews Sunday.

The document, posted repeatedly on the online forum 4chan immediately following the shooting, has been easily available on mainstream social media platforms. It spews racist, anti-immigrant and anti-Semitic views, extensively discussing the conspiracy theory that white people are being “replaced.” The document also discusses the rationale for the location of the shooting, with the author saying they selected a ZIP code with a high percentage of Black people that was reasonably close to their home.

The shooter visited the area on Friday

A day before the shooting, the alleged shooter visited the area of the supermarket for the first time, according to police.

“We have no information at all that he was here in Buffalo anytime before this,” Gramaglia said. “It appears right now, as we stand, that Friday was the first day that he would have been here.”

The first 911 call for the shooting came in around 2:30 p.m. on Saturday. Buffalo police responded at 2:31 p.m., according to Gramaglia.

Gramaglia also said the shooter used an AR-15 rifle and had an additional rifle and shotgun in his car.

State police visited the alleged shooter last June

Saturday was not Gendron’s first brush with police, authorities said Sunday.

Last June, state police investigated a “generalized threat” he made, according to Gramaglia. The threat, which Gramaglia said was not racist in nature, was reported by Gendron’s school, Susquehanna Valley High School.

"They investigated, they interviewed the subject, and they felt it was appropriate at that time to have that individual brought in for a mental health evaluation,” Gramaglia said during a news conference Sunday. “State police did their job to the fullest they could at that time."

The threat apparently did not rise to the level of federal attention.

On Sunday, FBI Special Agent in Charge Stephen Belongia said the alleged shooter was “not on the radar of the FBI” prior to Saturday’s events.

Hochul said she wants to crack down on social media platforms

Along with live streaming the attack on Twitch, the shooter’s purported manifesto makes mention of activity on online platform Discord, as well as message boards 4chan and 8chan. And the 180-page document quickly circulated on more mainstream social-media platforms in the hours after the attack.

It led Hochul, a Democrat, to criticize social-media platforms for not doing more to crack down on violent and racist content, such as the rhetoric contained in the manifesto.

In a round of national media interviews Sunday, Hochul repeatedly called on tech companies to do more to spot and remove hate speech – saying she wants to force the companies to prove to her that there’s nothing more they can do.

"This was all telegraphed,” Hochul said on NPR. “It was written out in a manifesto that was published on social media platforms. The information was there."

Representatives for Discord did not immediately return a message seeking comment Sunday.

Twitch released a statement saying the company has “a zero-tolerance policy against violence of any kind and works swiftly to respond to all incidents.”

“The user has been indefinitely suspended from our service, and we are taking all appropriate action, including monitoring for any accounts rebroadcasting this content,” the statement reads.

Samantha Faught, a Twitch spokesperson, said the alleged shooter’s live stream was removed two minutes after the violence began.

This story has been updated with additional information.