Two US Postal Service employees were shot dead Tuesday in a gun attack at a Tennessee post office, authorities said.

The suspected shooter opened fire at the East Lamar Carrier Annex in Memphis and then died of a self-inflicted gunshot wound.

US Postal Inspector Susan Link told reporters that both victims, as well as the shooter, were postal service employees. "There is no ongoing threat," she said.

"The FBI is working the scene and can confirm that the shooter is one of the three employees deceased by an apparent self-inflicted gunshot wound," said Lisa-Anne Culp, a spokeswoman for the FBI's Memphis field office, at the same press conference.

An investigation has been launched, she said.

Both Link and Culp declined to give further details about the shooting.

"The Postal Service is saddened at the events that took place today in Memphis," the USPS said in a statement. "Our thoughts are with the family members, friends and coworkers of the individuals involved."

Mass shootings and other gun violence are huge problems in the United States, issues that gun control advocates say are fueled by the prevalence of firearms and relatively lax gun laws.