The 18-year-old who killed 10 people and wounded three others at a supermarket in Buffalo, New York on Saturday wrote while at the Institute that he wanted to commit a mass shooting, The Wall Street Journal (WSJ) reported.
The newspaper, which cites an officer with knowledge of the investigation, claims that teachers informed the police.
Buffalo Police Commissioner Joseph Gramaglia acknowledged during a press conference Sunday that in June of last year, the attacker, identified as Payton Gendron, made a generalized threat, but not a specific threat directed at a particular place or person.
Gramaglia, who did not offer more details about the threat, said that the police investigated what happened, held an interview with him, and transferred him to a mental institution for evaluation.
According to the WSJ, he was released a day and a half later.
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On Saturday, Gendron drove from Conklin, a town 200 miles southeast of Buffalo, and parked in the parking lot of Tops supermarket at about 2:30 p.m. local time.
He then exited the vehicle armed, wearing a bulletproof vest, a helmet, and a camera with which he live-streamed the massacre on Amazon’s Twitch platform before turning himself in to police.
Authorities are investigating what happened as a terrorist attack and a hate crime based, among other things, on a manifesto that the young man apparently left written, in which he described himself as a communist in his youth.
Baptist Bishop Darius Pridgen said during a mass in honor of the victims that in the text Gendron, a white man, wrote that he wanted to kill all blacks.