After a white 18-year-old wearing military gear and live-streaming with a helmet camera opened fire with a rifle at a supermarket in Buffalo, killing 10 people and wounding three others, US president Joe Biden said racially motivated hate crime was “abhorrent to the very fabric of this nation”. Police said the attacker shot 11 Black and two white victims before surrendering to authorities in an assault he broadcast on the streaming platform Twitch. Later, he appeared before a judge in a paper medical gown and was arraigned on a first-degree murder charge. He pleaded not guilty. In a statement, Biden said: “We still need to learn more about the motivation for [the] shooting as law enforcement does its work, but we don’t need anything else to state a clear moral truth: A racially motivated hate crime is abhorrent to the very fabric of this nation.” Biden added: “Any act of domestic terrorism, including an act perpetrated in the name of a repugnant white nationalist ideology, is antithetical to everything we stand for in America. Hate must have no safe harbor. We must do everything in our power to end hate-fueled domestic terrorism.” Vice-President Kamala Harris said she was heartbroken by events. “What is clear is that we are seeing an epidemic of hate across our country that has been evidenced by acts of violence and intolerance. We must call it out and condemn it,” she said. The suspected gunman in Saturday’s attack on Tops Friendly Market was identified as Payton Gendron, of Conklin, New York, about 200 miles (320km ) south-east of Buffalo. It wasn’t immediately clear why Gendron had traveled to Buffalo and that particular grocery store. A clip apparently from his Twitch feed, posted on social media, showed Gendron 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, security guard Aaron Salter, a retired Buffalo police officer, fired multiple shots. A bullet hit the gunman’s bulletproof armor but had no effect, Gramaglia said. The gunman then killed the guard, the commissioner said, then stalked through the store shooting other victims. Police entered the store and confronted the gunman in the vestibule. He put his rifle to his own neck, but two officers talked him into dropping the gun, Gramaglia said. As Buffalo and the rest of the US began to mourn, details about the shooter and hours preceding the attack have started to emerge. The shooter had been under “medical” supervision for something he wrote in high school, authorities said. He arrived in Buffalo at least one day prior to the mass shooting, to conduct reconnaissance, police said. Gramaglia said on This Week With George Stephanopoulos that the shooter “was in the Buffalo area 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.” “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.” Twitch said in a statement that it ended Gendron’s transmission “less than two minutes after the violence started”. A law enforcement official told the Associated Press that investigators were looking into whether he had posted a manifesto online. Buffalo police declined to comment on the document, circulated widely online, that purports to outline the attacker’s racist, anti-immigrant and antisemitic beliefs, including a desire to drive all people not of European descent from the US. It said he drew inspiration the man who killed 51 people at two mosques in Christchurch, New Zealand, in 2019 and also called for the killing of London mayor Sadiq Khan. The video posted online also seemed to show a racial slur written on the weapon used. During an interview on This Week, New York governor Kathy Hochul was asked: “Had he been on the radar of law enforcement at all?” “Just as a high school student with respect to something he wrote in high school and was under the surveillance at the time with medical authorities,” Hochul said. Brown told CNN that “from reports that I’ve been hearing and that he did surveil this community, was scouting the supermarket, actually talked to some people in the area”. Hochul said authorities believe that he “targeted the busiest place at one of the busiest times”. CNN noted that this mirrored a line from the shooter’s seeming manifesto; the writer, claiming to be the shooter, allegedly wrote: “Zip code 14208 in Buffalo has the highest black percentage that is close enough to where I live.” Federal agents were also interviewing the shooters’ parents and had served multiple search warrants. The parents were reportedly cooperating with investigators. It also emerged that he had last year threatened a shooting at his high school and been sent for mental health treatment and an evaluation at hospital. An official with knowledge of the investigation told CNN that the suspect made comments following his arrest that showed clear hatred against the Black community. “The alleged shooter made it known he was targeting the Black community during the statements,” the network paraphrased this official as saying. “Tonight, the country mourns the victims of a senseless, horrific shooting in Buffalo, New York. The FBI and ATF are working closely with the Buffalo police department and federal, state, and local law enforcement partners,” US Attorney General Merrick B Garland said in a statement. “The justice department is investigating this matter as a hate crime and an act of racially-motivated violent extremism.” Among the dead was Ruth Whitfield, the 86-year-old mother of a retired Buffalo fire commissioner. “My mother was a mother to the motherless. She was a blessing to all of us,” former Fire Commissioner Garnell Whitfield told the Buffalo News. Community members gathered outside the Tops on Sunday morning for a prayer vigil. “This was domestic terrorism, plain and simple,” New York’s attorney general, Letitia James, said at the True Bethel church in Buffalo. “He was fed, each and each day, a steady diet of hate,” James also added. At the same church service, Hochul reportedly said: “I will say one thing… Lord forgive the anger in my heart.” Hochul said that the shooter’s gun, an AR-15, was purchased legally in the state. “The gun was purchased in a gun store in New York state legally, an AR-15. But what has made this so lethal, and so devastating for this community, was the high-capacity magazine that would have had to have been purchased elsewhere, that’s not legal in the state of New York,” Hochul told CNN. NAACP President Derrick Johnson issued a statement in which he called the Buffalo shooting “absolutely devastating”. “Hate and racism have no place in America,” he said. The Rev Al Sharpton called on the White House to convene a meeting with Black, Jewish and Asian leaders to demonstrate a federal commitment to combating hate crimes. In 2019, another white man, Patrick Crusius, drove across Texas to kill Hispanic people at a Walmart in the border city of El Paso and carried out a gun attack that left 23 people dead.