A white teenager who fatally shot 10 people in a racist attack at a New York grocery store in a black neighbourhood was taken into custody and given a mental health evaluation a year ago, but was released after roughly a day, authorities say.
The suspect, Payton Gendron, 18, surrendered to police on Saturday at the Buffalo, New York, grocery store after what authorities called an act of "racially motivated violent extremism."
A manifesto allegedly written by Gendron describes the supermarket as being in a ZIP code with "the highest Black percentage that is close enough to where I live."
"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.
Eleven people struck by gunfire were black and two were white, officials said. The racial breakdown of the dead was not made clear.
Mr Gramaglia told reporters that Gendron had been taken into custody and given a mental evaluation over a day and a half last June but was released.
New York State police said they had been called to a high school in Gendron's hometown of Conklin, New York, near the Pennsylvania border, on 8 June, 2021, in response to a 17-year-old student making a threatening statement.
Without identifying Gendron, police said the student was taken into custody and given a mental health evaluation at a hospital. He was not charged criminally.
New York Governor Kathy Hochul told ABC News on Sunday that an investigation would focus on what could have been done to stop Gendron, since he had advertised his views online and had been on authorities' radar.
"I want to know what people knew and when they knew it," she said.
Authorities said Gendron drove to Buffalo from his home several hours away to launch the attack, which he broadcast in real-time on social media platform Twitch, a live video service owned by Amazon.com.
He then opened fire at the Tops grocery store using a gun that he legally purchased but had illegally modified a high-capacity magazine, Ms Hochul said.
People gather outside of Tops market on 15 May, 2022 in Buffalo, New York. Yesterday a gunman opened fire at the store, killing 10 people and wounding another three. Suspect Payton Gendron was taken into custody and charged with first degree murder. Source: Getty / Scott Olson/Getty Images
Nearby, at the True Bethel Baptist Church, a reverend led a mournful service for a large crowd of worshippers, including some family of the victims and some who had been at the store at the time of the shooting.
Gendron was arraigned hours after the shooting in state court on first-degree murder charges. He entered a plea of not guilty and is scheduled to return to court on 19 May.
