Grieving residents from the US city of Buffalo held vigils Sunday after a white gunman who officials have deemed "pure evil" shot dead 10 people at a grocery store in a racially-motivated rampage.

Buffalo, New York police commissioner Joseph Gramaglia told reporters the 18-year-old suspect did "reconnaissance" on the predominantly Black area surrounding Tops Friendly Market and drove there from his hometown of Conklin, more than 200 miles (322 kilometers) away.

Wearing heavy body armor and wielding an AR-15 assault rifle, the shooter killed 10 people and wounded three others -- almost all of them Black -- before threatening to turn the gun on himself. Police talked the gunman down before arresting him.

The suspect, identified as Payton Gendron, was arraigned late Saturday on a single count of first-degree murder and held without bail, the Erie County district attorney's office said. He pleaded not guilty.

"The evidence that we have uncovered so far makes no mistake that this is an absolute racist hate crime" and will be prosecuted as such, Gramaglia said Sunday, adding the shooter also had a rifle and shotgun in his car.

Buffalo Mayor Byron Brown was unequivocal about the shooter's motivations: "This individual came here with the express purpose of taking as many Black lives as he possibly could."