The 18-year-old alleged gunman suspected of killing 10 people and injuring three others at a Buffalo, New York, supermarket on Saturday was 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.
A state police spokesman did not release a name to NBC News but said the subject of the investigation was 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 the suspect was evaluated and released but no further complaints were made.
“There was nothing picked up on the state police intelligence, nothing picked up on the FBI intelligence,” Gramaglia said during a Sunday news conference.
He added that police are limited in how far they can take investigations and monitoring of social media, saying not everything constitutes violations of the law.
Gramaglia noted that this will be a “lengthy” investigation on both the federal and local level. He called the attack — in which where 11 of 13 people 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 noted during the news conference that the investigation into the suspect occurred prior to her time in office but 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 rifle used in the attack was legally purchased in New York, a senior law enforcement official said. A hunting rifle and shotgun were also found at the scene. 
In addition to the guns, the suspect had multiple 30-round magazines on his person at the time of the shooting, according to the official. Ammunition magazines that hold more than seven bullets were outlawed in New York state in 2013 as part of a larger gun control legislation.
It’s unclear where the suspect obtained the 30-round magazines.
A search warrant was granted for state officials Saturday night but investigators held off searching the suspect’s home until a federal warrant could also be issued Sunday morning.
A judge remanded the suspect into custody without bail during an arraignment Saturday evening in Buffalo City Court on one count of murder in the first degree. A felony hearing was scheduled for Thursday morning.
Erie County Sheriff John Garcia said that the suspect is being continuously monitored on suicide watch and will be given mental health services where needed.
A senior law enforcement official said authorities are working to authenticate a racist manifesto posted last week with the suspect’s personal information. NBC News confirmed the document was posted to Google Docs two days prior to the shooting.
In the alleged manifesto, the suspect appears to self-describe as a racist, white supremacist, and anti-Semite. The document espouses the “Great Replacement” conspiracy theory frequently pushed by white supremacists, a racist doctrine that white Americans are being “replaced” by non-white immigrants.
President Joe Biden called the suspect a “lone gunman armed with weapons of war and hate filled soul.”
“The Justice Department has stated publicly that it’s investigating the matter as a hate crime, racially motivated act of white supremacy and violent extremism,” Biden said Sunday.
Jennifer Tookes was inside the Tops supermarket when she heard shots ring out from the front of the store. She ran through the deli, exiting through two doors as she heard the gunman make his way to the back of the store.
Tookes said that she saw “three bodies laying outside in the parking lot” as she made her way outside.
When she got to her car, Tookes tried to call her cousin who was also shopping with her at the time. They had separated and were in different aisles when the shots rang out.
She later learned, she said, that her cousin hid in the store’s freezer until the gunfire stopped.
“I’ll have this in my head for the rest of my life,” Tookes said. “I don’t know if I’ll ever be able to go into a grocery store or a store.”
