Four US Marines have been killed in shootings at two US Navybuildings in Chattanooga, Tennessee.
The district lawyer said the two incidents were being investigated as an "act of domestic terrorism".
Shots were fired at a US Navy reserve centre and at a recruitment office about seven miles (10 km) away.
Chattanooga city police said it was the same gunman at both locations and confirmed that the "active shooter" had been killed.
The US Marines confirmed in a statement that there were "four Marine fatalities" at the Navy and Marine Corps Reserve Centre in Chattanooga.
City Mayor Andy Berke tweeted: "Horrific incident in our community... Prayers to all those affected."
FBI agent Ed Reinhold, who is leading the investigation, said the first shooting occurred around 10:45 local time (14:45 GMT) at the recruitment centre in the east of the city.
After opening fire on the building, the gunman then fled the scene in a Ford Mustang and was pursued by Chattanooga police, he told reporters.
The gunman was eventually killed by police near the US Navy reserve centre on Amnicola Highway, about a five minute drive away.
The main road was cordoned off by police and the nearby Chattanooga State University was briefly placed on lockdown.
Eyewitnesses reported seeing a gunman firing from inside a car outside the recruitment centre.
One told CNN she heard "really loud noises" and later saw a white man with a "high-powered rifle".
Gina Mule, who works at a local restaurant, said the gunman was driving a convertible silver Mustang car. "A lot of shots were fired," she added.
A statement from the White House said President Barack Obama has been briefed on the incident.