The suspect died in a hospital following the mid-afternoon incident on Thursday (March 31) in Richmond, Virginia, State Police spokesman Corinne Geller said in a statement.
A trooper he allegedly shot at the city's Greyhound bus station has been hospitalized with life-threatening injuries, she added.
Two civilians were also hurt in the incident but were expected to survive.
Witnesses said that police cars and ambulances rushed to the station.
Ms Geller said the suspect pulled out a firearm when approached by the trooper and proceeded to shoot the officer. Two other troopers nearby returned fire, AFP reported.
Greyhound said it was closing the station until further notice and was cooperating with authorities as they investigate what happened.
Virginia Governor Terry McAuliffe said in a statement that he had been in contact with the mayor of Richmond and the head of the Virginia State Police and offered any resources needed to respond to the situation.
Virginia has laws favorable to carrying guns and the National Rifle Association, the powerful pro-gun lobby, is based in the state.