A gunman shot a Virginia state trooper at a Greyhound bus terminal in Richmond Thursday before he was shot dead by two other troopers, according to a police spokeswoman.

The trooper's injuries were life-threatening, according to Virginia State Police spokeswoman Corie Geller.

Two civilians were hurt in the incident, though it was not clear if they had been shot, Geller said.

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Geller added that the shooter approached the trooper, who was dressed in an "identifiable" outfit before they had a conversation and the man drew a gun and opened fire.

Initially, State Police had said in a news release that two troopers were taken to a hospital, but Geller later told reporters that only one had been hurt.

State police were holding a training exercise at the time the shots rang out, WTVR reported.

"The first thing we saw were police cars flying by, then officers in riot gear ruing with weapons," Vincent Smith, an employee at a nearby U-Haul storage facility, told the Richmond Times-Dispatch. Other witnesses reported hearing as many as 10 shots.

Virginia Commonwealth University Medical Center confirmed that multiple patients from the shooting scene were brought to the hospital.

The bus station is three miles north of VCU's downtown Richmond campus, and across the street from The Diamond, the city's minor league baseball stadium.

Vincent Smith told the Associated Press he was working next door to the Greyhound station when he heard sirens and saw police cars buzzing by.

"The police units just poured in like a river," said Smith, who works at the U-Haul Moving and Storage facility. "I went to the end of the lot and there must have been 30 units just a block away."

Smith said he saw police officers carrying shields and assault weapons. An officer came by and ordered him and his co-workers to stay inside and lock the doors until they're told it was safe again. By late afteoon, he said he had been locked inside for about an hour and a half.

Greyhound said in a service advisory on its website that the bus station will be closed until further notice, and that service in and out of Richmond has been canceled.

Greyhound added that it will re-route customers where possible.

Officials from the Bureau of Alcohol, Tobacco, Firearms and Explosives told Fox News that agents from its Richmond field office are on scene at the bus station to assist authorities in the investigation of the shooting there.

Fox News was also told by an official that the FBI’s Richmond field office is also assisting in a support capacity, while the Virginia State Police is leading the investigation.

Virginia Gov. Terry McAuliffe said in a statement Wednesday he is offering whatever state resources "may be necessary" to respond to the situation.

"Our public safety team and I will continue to monitor the situation and support State Police and local authorities in their response and investigation of this incident." he said.

City Councilwoman Reva Trammell called it "the saddest day in the city of Richmond."

"State troopers doing their job and iocent people shot," she said. "Why? This was a senseless act."

Fox News' Matt Dean and The Associated Press contributed to this report.