The FBI said cellphone records and a common modus operandi link one man to three recent bank robberies — an attempt in Atlanta, another robbery in Tupelo, Miss., that left a police officer dead and a third in Phoenix that left the bank robber dead.

Phoenix police identified the suspect as Mario Edward Garnett, 40, who is from the Midwest and served four years in the U.S. Army.

At a news conference in Tupelo on Sunday morning, Jackson, Miss., FBI special agent in charge Daniel McMullen said there were similarities between the three robberies, including the clothing worn by the suspect, the object used to prop open a door, what the suspect said during the robberies and the robber’s overall MO.

McMullen said the FBI obtained a court order to review the suspect’s phone records, revealing that his cellphone was in Atlanta, Tupelo and Phoenix during each of the robberies.

“This investigation is not over,” McMullen said.

Garnett, who had been the subject of a nationwide manhunt for six days, was shot and killed outside a Phoenix bank he had just robbed, according to the FBI.

News of Garnett’s death came just a day after the FBI announced a link between the Atlanta incident and a deadly shooting that killed one Tupelo officer and injured a second.

Around 9:30 a.m. Monday, a man wearing a black ski mask and armed with a semi-automatic handgun entered the Bank of America in the 2600 block of Piedmont Road and demanded cash, according to Stephen Emmett, spokesman for the FBI Atlanta office.

“The robber, unsuccessful in his robbery attempt, made the same demand from a customer at an ATM machine located in the vestibule of the bank,” Emmett said in an emailed statement. “After obtaining an undisclosed amount of money from the customer, the robber departed the bank without further incident.”

Investigators believe the same suspect then drove in a grey sedan to Tupelo, where he allegedly shot two officers during a bank robbery Monday afternoon. Kevin “Gale” Stauffer, 38, was killed and Joseph Maher, 26, was critically injured.

Stauffer’s funeral was held Friday and Maher’s condition had improved, according to Mississippi media reports.

The suspect was described as a male wearing a black ski mask, a grey and white long-sleeve shirt with an “Aztec” print, black gloves, and light or grey tennis shoes, possibly Chuck Taylor Converse style, the FBI said. He was armed with a black semi-automatic handgun, possibly a Sig Sauer .45 caliber.

On Saturday around 10 a.m., a man matching the suspect’s description entered a Phoenix bank, displayed a handgun and then filled a bag with cash from the vault, the FBI said.

“The robber encountered a Phoenix police detective outside the bank and shots were fired,” the FBI said in an emailed statement. “The bank robber was shot and killed in the exchange.”

In 2011, Garnett was sentenced to eight months in federal prison for a post on the White House website threatening to kill President Barack Obama, according to a report by The (Oklahoma City) Oklahoman on its website NewsOK.com. The report said Garnett was ordered to get mental health care upon his release.

“He can’t own a gun,” the report also said.

— Staff writer Alexis Stevens contributed to this report.