A civilian worker at the Fort Knox US army base has been shot dead in a parking lot of the Kentucky complex, with authorities saying the killer remained at large.
Authorities said the shooting outside the army's Human Resources Command headquarters was "not a random act". It took place less than two weeks after a US marine shot dead two colleagues at a Virginia base.
The victim, an employee of the human resources command, was transported by ambulance to Ireland army community hospital where he was pronounced dead.
"Special Agents from the US army Criminal Investigation Command are investigating a personal incident and not a random act of violence," said Chris Grey, a spokesman for the independent army investigative agency.
Fort Knox's gates were locked to all inbound and outbound traffic as a standard security measure, the army said. The main gate was reopened an hour later.
The Fort Knox army base, near Louisville, is home to more than 40,000US military personnel, family members and civilian employees, and is adjacent to the United States Bullion Repository, also known as Fort Knox.
Mary Trotman, an FBI spokeswoman in Louisville, said two agents were sent to Fort Knox to assist with the probe. The army said police were "interested in speaking" with a man who may be using a black Yamaha motorcycle for transportation.
Police in surrounding jurisdictions had earlier been asked by Fort Knox officials to be on the lookout for a man driving a four-door brown car with tinted windows who may have driven off the base, said Bryce Shumate, spokesman for the police department in nearby Radcliff.
The incident came less than two weeks after a US marine shot two colleagues to death at the Marine Corps base in Quantico, Virginia, before killing himself. In February local media reported that a soldier and his wife died of gunshot wounds at their home in Fort Knox in what the army said was the result of a domestic dispute.