The 18-year-old man suspected of killing 10 people and injuring three others at a Buffalo, New York, supermarket on Saturday had been previously investigated for making a violent statement.
Payton Gendron was investigated by New York State Police last year for making a threatening statement in June, when he was a minor, a law enforcement official said. The threat was about wanting to carry out a shooting, according to a different senior law enforcement official.
A state police spokesman, who did not release a name to NBC News, said the subject of the investigation had been transported to the hospital for a mental health evaluation at the time and was not charged with a crime.
Buffalo Police Commissioner Joseph Gramaglia said that the suspect was evaluated and released and no further complaints were made.
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"There was nothing picked up on the state police intelligence, nothing picked up on the FBI intelligence," Gramaglia said at a news conference Sunday.
He added that police are limited in how far they can take investigations and in monitoring social media, saying not everything constitutes a violation of the law.
Gramaglia said it would be a "lengthy" investigation on both the federal and local levels. He called the attack — in which 11 of 13 people who were shot were Black — a clear hate crime.
"The evidence we uncovered so far makes no mistake that this is an absolute racist hate crime," Gramaglia said. "It will be prosecuted as a hate crime. This is someone who has hate in their heart, soul and mind."
New York Gov. Kathy Hochul said at the news conference that the suspect was investigated before her time in office and that she would look for answers into what happened.
"I understand the First Amendment rights very well. I have no intention of impinging upon them," Hochul said. "However, hate speech is not protected. ... There are parameters if you're going to be inciting people to violence. That's not protected."
Officials said the suspect streamed the attack on Twitch, a platform used by gamers to livestream as they play. A Twitch spokesperson confirmed that the stream was removed "less than two minutes after the violence started."
The assault-style rifle used in the attack was legally purchased in New York, a senior law enforcement official said. A hunting rifle and a shotgun were also found at the scene.
In addition to the guns, the suspect had multiple 30-round magazines on him, the official said. Ammunition magazines that hold more than seven bullets were outlawed in New York state in 2013 as part of larger gun control legislation.