Photo: The Canadian Press

Police secure a perimeter after a shooting at a supermarket, Saturday, May 14, 2022, in Buffalo, N.Y. (AP Photo/Joshua Bessex)

UPDATE 10:45 a.m.

The white 18-year-old who shot and killed 10 people at a Buffalo supermarket had researched the local demographics while looking for places with a high concentration of Black residents, arriving there at least a day in advance to conduct reconnaissance, law enforcement officials said Sunday.

Authorities said the gunman shot, in total, 11 Black people and two white people Saturday in a rampage motivated by racial hatred that he broadcast live.

“This individual came here with the express purpose of taking as many Black lives as he could,” Buffalo Mayor Byron Brown said at a news conference Sunday.

The shooter, identified as Payton Gendron, had previously threatened a shooting at his high school last June, a law enforcement official told The Associated Press. Buffalo Police Commissioner Joseph Gramaglia said the then-17-year-old was brought in for a mental health evaluation afterward.

Meanwhile, federal authorities were still working to confirm the authenticity of a racist 180-page manifesto that detailed the plot and identified Gendron by name as the gunman, the law enforcement official told the AP. But the shooting — the latest act of mass violence in a country unsettled by racial tensions, gun violence and a recent spate of hate crimes — left local residents shattered.

It also prompted New York Gov. Kathy Hochul, a Buffalo native, to demand the technology industry take responsibility for its role in propagating hate speech.

Hochul told ABC that the heads of technology companies “need to be held accountable and assure all of us that they’re taking every step humanly possible to be able to monitor this information."

“How these depraved ideas are fermenting on social media — it’s spreading like a virus now,” she said Sunday, adding that a lack of oversight could lead others to emulate the shooter.

Twitch said in a statement that it ended Gendron’s transmission “less than two minutes after the violence started.”

Screenshots purporting to be from the live Twitch broadcast appear to show a racial epithet scrawled on the rifle used in the attack, as well as the number 14, a likely reference to a white supremacist slogan.

A preliminary investigation found Gendron had repeatedly visited sites espousing white supremacist ideologies and race-based conspiracy theories and extensively researched the 2019 mosque shootings in Christchurch, New Zealand, and the man who killed dozens at a summer camp in Norway in 2011, the law enforcement official, who spoke on condition of anonymity, told AP.

The manifesto posted online and purportedly written by Gendron, outlined a racist ideology rooted in a belief that the United States should belong only to white people. All others, the document said, were “replacers” who should be eliminated by force or terror. The attack was intended to intimidate all non-white, non-Christian people and get them to leave the country, it said.

It wasn’t immediately clear why Gendron had traveled about 200 miles (320 kilometers) from his Conklin, New York, home to Buffalo and that particular grocery store, but investigators believe Gendron had specifically researched the demographics of the population around the Tops Friendly Market, the official said. The market is located in a predominantly Black neighborhood.

In a Sunday interview with ABC, Gramaglia said that Gendron had been in town “at least the day before.”

“It seems that he had come here to scope out the area, to do a little reconnaissance work on the area before he carried out his just evil, sickening act,” Gramaglia said.

Gendron had appeared on the radar of police last year after he threatened to carry out a shooting at Susquehanna High School around the time of graduation, the official said. New York State Police said troopers were called to the Conklin school on June 8, 2021, for a report that a 17-year-old student had made threatening statements.

ORIGINAL 6:30 a.m.

A white 18-year-old wearing military gear and livestreaming with a helmet camera opened fire with a rifle at a supermarket in Buffalo, killing 10 people and wounding three others Saturday in what authorities described as “racially motived violent extremism.”

The gunman wore body armor and military-style clothing during the attack on mostly Black shoppers and workers at Tops Friendly Market. For at least two minutes, he broadcast the shooting live on the streaming platform Twitch before the service ended his transmission.

Police said he shot 11 Black victims and two who were white before surrendering to police. Later, he appeared before a judge in a paper medical gown and was arraigned on murder charges.

“It is my sincere hope that this individual, this white supremacist who just perpetrated a hate crime on an innocent community, will spend the rest of his days behind bars. And heaven help him in the next world as well,” said Gov. Kathy Hochul, speaking near the scene of the attack.

The suspected gunman was identified as Payton Gendron, of Conklin, New York, about 200 miles (320 kilometers) southeast of Buffalo.

It wasn't immediately clear why Gendron traveled to Buffalo to stage the assault. A clip apparently from his Twitch feed, posted on social media, showed him arriving at the supermarket in his car.

The gunman shot four people outside the store, three fatally, said Buffalo Police Commissioner Joseph Gramaglia. Inside the store, a security guard who was a retired Buffalo police officer fired multiple shots, but a bullet that hit the gunman’s bulletproof vest had no effect, Gramaglia added.

The gunman then killed the guard, the commissioner said, then stalked through the store shooting other victims.

“This is the worst nightmare that any community can face, and we are hurting and we are seething right now,” Buffalo Mayor Byron Brown said at the news conference. “The depth of pain that families are feeling and that all of us are feeling right now cannot even be explained.”

Police entered the store and confronted the gunman in the vestibule.

“At that point the suspect put the gun to his own neck," Gramaglia said. Two officers talked him into dropping the gun, the commissioner said.

At the earlier news briefing, Erie County Sheriff John Garcia pointedly called the shooting a hate crime.

“This was pure evil. It was straight up racially motivated hate crime from somebody outside of our community, outside of the City of Good neighbors ... coming into our community and trying to inflict that evil upon us," Garcia said.

Witnesses Braedyn Kephart and Shane Hill, both 20, pulled into the parking lot just as the shooter was exiting. They described a white male in his late teens or early twenties sporting full camo, a black helmet and what appeared to be a rifle.

“He was standing there with the gun to his chin. We were like what the heck is going on? Why does this kid have a gun to his face?” Kephart said. He dropped to his knees. “He ripped off his helmet, dropped his gun, and was tackled by the police.”

Tops Friendly Markets released a statement saying, “We are shocked and deeply saddened by this senseless act of violence and our thoughts and prayers are with the victims and their families.”

The shooting came little more than a year after a March 2021 attack at a King Soopers grocery in Boulder, Colorado, that killed 10 people. Investigators have not released any information about why they believe the man charged in that attack targeted the supermarket.

NAACP President Derrick Johnson issued a statement in which he called the Buffalo shooting “absolutely devastating.”

“Our hearts are with the community and all who have been impacted by this terrible tragedy. Hate and racism have no place in America. We are shattered, extremely angered and praying for the victims’ families and loved ones,” he added.

The Rev. Al Sharpton called on the White House to convene a meeting with Black, Jewish and Asian leaders “to underscore the Federal government (is) escalating its efforts against hate crimes.”

At the White House, Press Secretary Karine Jean-Pierre said President Joe Biden was receiving regular updates on the shooting and the investigation and had offered prayers with the first lady for the victims and their loved ones.

“The president has been briefed by his Homeland Security advisor on the horrific shooting in Buffalo, N.Y., this afternoon. He will continue to receive updates throughout the evening and tomorrow as further information develops," she said.

Attorney General Merrick Garland was briefed on the shooting, Justice Department spokesperson Anthony Coley said.

More than two hours after the shooting, Erica Pugh-Mathews was waiting outside the store, behind police tape.

“We would like to know the status of my aunt, my mother's sister. She was in there with her fiancé, they separated and went to different aisles," she said. "A bullet barely missed him. He was able to hide in a freezer but he was not able to get to my aunt and does not know where she is. We just would like word either way if she’s OK.”