A gunman fatally shot a Virginia state trooper at a busy bus station in the US city of Richmond before he was shot dead by two other troopers.
Two civilians were also shot but were expected to recover.
Trooper Chad Dermyer, 37, died after being shot multiple times, according to Virginia State Police Superintendent Colonel Steven Flaherty.
State Police spokeswoman Corinne Geller said the civilians' injuries were not life-threatening.
A small army of law enforcement officers in tactical gear and dozens of cruisers and emergency response vehicles flooded to the station, located in an area that includes a minor league baseball stadium and a variety of shops and restaurants.
Najee Wilson, 18, of Newark, New Jersey, said his bus was pulling up to the station when he heard three gunshots and saw people running out of the building.
"We heard a lot of people screaming," he said. "It definitely was a scary experience."
The teenager, who was en route to Atlanta, was among about 200 travellers waiting to board buses at a staging area set up near the bus station after the shooting.