A gunman shot and killed at least six people in a Walmart store late Tuesday in the U.S. state of Virginia, police and city officials said, adding that the shooter too is dead.

The store in Chesapeake was busy just before the shooting Tuesday night with people stocking up ahead of the Thanksgiving holiday, a shopper told a local TV station.

Officer Leo Kosinski couldn't say how the shooter died but said that he didn't believe police fired shots. It was not clear who the shooter was or what their motive might be.

"I am devastated by the senseless act of violence that took place late last night in our city," Mayor Rick W. West said in a statement posted on the city's Twitter account Wednesday. "Chesapeake is a tight-knit community and we are all shaken by this news."

Joetta Jeffery told CNN she received text messages from her mother who was inside the store during the shooting. Her mother, Betsy Umphlett, was not injured.

"I'm crying, I'm shaking," Jeffery said. "I had just talked to her about buying turkeys for Thanksgiving, then this text came in."

A database run by The Associated Press, USA Today and Northeastern University that tracks every mass killing in America going back to 2006 shows this year has been especially bad. The U.S. has now had 40 mass killings so far this year, second to the 45 that occurred for all of 2019. The database defines a mass killing as at least four people killed, not including the killer.

The attack at the Walmart came three days after a person opened fire at a gay nightclub in Colorado, killing five people and wounding 17. Earlier in the year, the country was shaken by the deaths of 21 when a gunman stormed an elementary school in Uvalde, Texas.