US Walmart gunman 'left phone death note'

A Walmart supervisor who killed six co-workers at a store in Virginia bought a handgun the day of the shooting and left a rambling note on his mobile phone in which he railed against other employees he felt had mocked and betrayed him.

Information on the firearm purchase and note was released by the city of Chesapeake on Friday in an update on its investigation into the shooting, in which 31-year-old Andre Bing opened fire on other workers before turning the gun on himself.

In a separate shooting on Friday, Walmart said it had evacuated a supercentre in Lumberton, North Carolina.

One person was shot at the store and police were searching for a suspect, according to a local CBS affiliate.

Lumberton police did not immediately respond to a request for comment.

Also Friday, law enforcement officials were investigating threatening phone calls made to two Walmart stores in Virginia Beach, about 32km east of Chesapeake, according to police.

Bing, an overnight shift team leader, was armed with a handgun when he shot some but not all of the employees assembled in a break room prior to their shift on Tuesday, witnesses and police said, raising the prospect he targeted individuals.

In a search of his home, investigators found ammunition and various items related to the 9mm handgun, including a receipt, according to the update from Chesapeake, a city of 251,000 people about 320km south of Washington DC.

"The gun was legally purchased from a local store on the morning of Tuesday, November 22. He had no criminal history," the city said in a statement on Friday.

In his note, Bing made reference to an unspecified work failure on his part and perceived slights from co-workers he felt were mocking him.

He said he believed his phone had been hacked and "was giving the worst feeling imaginable".

"The associates gave me evil twisted grins, mocked me and celebrated my downfall the last day," he wrote.

"That's why they suffer the same fate as me."

Bing also wrote in the document titled "death note" that he planned to spare a person, whose name was redacted, because she had a special place in his heart, citing his own mother's death from cancer.

Asked to comment on Bing's note, Walmart said in a statement: "There is nothing that can justify taking innocent lives. Our focus continues to be on the families who are grieving and supporting our associates through this difficult time."

In addition to the seven dead, including Bing, two people are being treated in hospital.

One is in critical condition and one's condition is improving, the city said.

The victims ranged in age from a teenage boy to a 70-year-old man.