By Jenna Zucker and Gabriella Borter
BUFFALO, N.Y. (Reuters) -A white teenager who killed 10 people in a racist attack at a western New York grocery store in a Black neighborhood had been taken into custody last year and given a mental health evaluation after making a threat at his high school, authorities said.
New details, including the previous threat, emerged on Sunday that provided a fuller portrait of the suspect, Payton Gendron, 18, and his assault on a Buffalo supermarket that authorities described as an act of "racially motivated violent extremism."
"The evidence that we have uncovered so far makes no mistake this is an absolute racist hate crime that will be prosecuted as a hate crime," Buffalo Police Commissioner Joseph Gramaglia told reporters on Sunday.
Gendron surrendered to police after Saturday's shooting of 13 people, 11 of whom were Black. He has been charged with first-degree murder - which carries a maximum penalty of life in prison without parole in New York - and has pleaded not guilty.
Authorities said on Sunday that Gendron had driven to Buffalo from his home several hours away a day before the attack to do "reconnaissance" on the area. On Saturday afternoon he drove to the Tops Friendly Market, where he commenced an assault that he broadcast in real time on the social media platform Twitch, a live video service owned by Amazon.com.
Dressed in tactical gear, Gendron opened fire with a semi-automatic rifle that he had purchased legally, but then modified illegally. Authorities found two other guns - a rifle and a shotgun - in his car.
Gramaglia told reporters that Gendron had appeared on the radar of local law enforcement last June, when police detained him after he made a "generalized" threat at his high school. Gendron was given a mental health evaluation at the time, but was released after a day and a half.
New York Governor Kathy Hochul told ABC News on Sunday that an investigation would focus on what could have been done to stop the teenager, who appeared to have advertised a slew of violent, racist views online.
"I want to know what people knew and when they knew it," she said.
President Joe Biden and first lady Jill Biden will visit Buffalo on Tuesday, the White House said in a statement.
"Our hearts are heavy once again but our resolve must not waver; we must work together to address the hate that remains a stain on the soul of this nation," Biden said in a Twitter post.
A 180-page manifesto that circulated online, believed to have been authored by Gendron, outlined "The Great Replacement Theory" - a racist conspiracy theory that white people are being replaced by minorities in the United States and other countries.
Another document online that appeared to have been written by Gendron sketched out a to-do list for the attack, including cleaning the gun and testing the livestream.
A spokesperson for the Erie County district attorney's office declined to comment on the documents.
On Sunday, several dozen community members held an emotional vigil for the victims outside the store, where Sharon Doyle, a 55-year-old security guard with Erie County Public Library, led a chant of "Black Lives Matter, my life matters."
"We all go in this Tops. I was scared to even go to Walmart last night," Doyle said. "I have to go to work tomorrow and I’m terrified."
Nearby, at the True Bethel Baptist Church, a reverend led a mournful service for a crowd of worshipers, including some family of the victims and some who had been at the store at the time of the shooting.
One was Charles Everhart Sr., 65, whose grandson Zaire Goodman, 20, worked at the store. Goodman was shot in the neck but survived.
"He was pushing the carts back to the store and he was one of the first to get hit," Everhart said.
The Buffalo shooting follows other racially motivated mass murders in recent years, including a Pittsburgh synagogue attack that left 11 dead in October 2018, and the Atlanta spa shootings in March 2021 in which a white man killed eight people, targeting Asians.
Stephen Belongia, the FBI special agent in charge of the bureau's Buffalo field office, said the attack would be investigated both as a hate crime and as an act of "racially motivated violent extremism" under federal law.
Hochul, meanwhile, said she was dismayed that the suspect managed to live-stream his attack on social media, which she blamed for hosting a "feeding frenzy" of violent extremist ideology.
"These outlets must be more vigilant in monitoring social media content," she said.
Social media and streaming platforms like Twitch, which said it removed the stream after less than two minutes, have grappled with controlling violent and extremist content for years.
"The user has been indefinitely suspended from our service, and we are taking all appropriate action, including monitoring for any accounts rebroadcasting this content," a Twitch spokesperson said.
(Reporting by Jenna Zucker in Buffalo, New York; additional reporting by Kanishka Singh, Doina Chiacu, Sarah N. Lynch, Gabriella Borter, Ken Li and Tyler Clifford; editing by Paul Thomasch, Lisa Shumaker and Daniel Wallis)