The 18-year-old man who shot and killed 10 people at a Buffalo supermarket Saturday afternoon was motivated by hate, according to police, and it is fueling fear and concern among Long Island's Black communities about this growing threat.

The Tops Friendly Market where Payton Gendron is accused of opening fire with an assault weapon is in the heart of Buffalo's Black community. Police say 11 of the 13 people shot were Black.

Prior to the deadly shooting, Gendron allegedly wrote and posted a manifesto filled with white supremacist messaging.

Authorities say Gendron outlined specific plans to attack Black people and repeatedly cited the "Great Replacement" theory, which claims that Caucasians are being replaced in their countries by people of color and that it will lead to their extinction.

Maryann Ford, of Uniondale, says she is afraid to go to the supermarket and other places where there are crowds. She is calling on county officials to step up security measures in her neighborhood.

On Sunday morning, a heavy police presence was outside Antioch Baptist Church, while parishioners were attending Sunday service. The Nassau County executive and police commissioner say they are intensifying patrols at houses of worship and some businesses in the wake of the Buffalo shooting.

Officials also say the public can also play a role in preventing hate crimes, and further affirm the motto "if you see something, say something."

"If you know people in the community that are like that, please call the tip hotline or you can call your local precinct," said Nassau Police Commissioner Patrick Ryder.