The suspect in the supermarket shooting in Buffalo, New York, that left 10 dead is an 18-year-old who previously threatened violence against his high school, authorities said.

Payton Gendron of Conklin, New York, drove more than three hours to a grocery store Saturday and shot 13 people, killing 10. Authorities believe the assault was an intentional attack on members of a predominantly Black upstate New York neighborhood.

Eleven of the 13 people who were shot were Black.

Gendron was identified in the deadly attack Saturday and was charged with one count of murder. Officials said they would weigh additional charges in the coming days. 

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Meanwhile, federal agents on Sunday were working to confirm the authenticity of a 180-page racist manifesto that was posted online and identified Gendron by name as the gunman, a law enforcement official told The Associated Press on Sunday.

Here’s what we know about the suspect: 

Suspect had previously threatened his high school

Gendron threatened an attack at his high school last year, resulting in a referral for a mental health evaluation, a law enforcement official told USA TODAY on Sunday. The incident was reviewed by state authorities at the time.

The official, who was not authorized to comment publicly, said the suspect’s parents were cooperating with authorities.

New York State Police said troopers were called to the Conklin school last June for a report that the then 17-year-old student had made threatening statements. He spent a day and a half at the hospital before being released, authorities said, and then had no further contact with law enforcement.