Authorities say 18-year-old Payton Gendron had been planning the Buffalo shooting for months.

Police say he posted on sites like 4chan that he selected that particular zip code because it had the highest percentage of Blacks near him. Police are calling the Buffalo shooting a hate crime.

"[It] has all kinds of crazy people on there, discussing, you know, all kinds of different aspects of potential threats and such, and they are anonymous," said criminal justice expert Kenneth Gray, from the University of New Haven.

Gray says it's not illegal to post on sites like 4chan and because the posts are anonymous they can't be traced.

He says Gendron was already on law enforcement's radar after he had plans to shoot up his high school.

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"Law enforcement can be aware of the fact that this person is a potential threat, but they can't take active measures against them until they do something that is illegal," said Gray.

Gray says the pandemic has definitely influenced many of these racially or ethnically motivated violent extremists.

"COVID allows for people to be isolated and to be able to stew in their own thoughts at the time and that might have helped…causing the extreme thoughts to percolate to the top," said Gray.

Gendron has pleaded not guilty to a first degree murder charge with an assault weapon. He's under suicide watch.

Police say Gendron also planned to target another large superstore.