VCU Medical Center in Richmond said multiple patients from the shooting were brought to the center and declined to provide additional information at this time.
Greyhound said in a statement that their station in Richmond was closed until further notice and that they were actively working with authorities.
Witness Brendan Hamilton told NBC affiliate WWBT that he first heard two loud gunshots as he was about to enter the bus station.
Then "there were five, maybe 10 more after that," Hamilton said of the gunfire.
He saw people running from the station and left "as fast as I could."
Sarah Newman, 22, of Nashville, Tenn., said she was waiting about 30 feet from the front door of the station, waiting to pick up friends, when she heard a commotion inside.
"We heard a lot of yelling inside and we saw a few people run out, then we saw a bunch of police cars come in," she said. "They brought out the trooper and the other victims ... He had blood all over him and his eyes were lifeless."
Newman said her thoughts turned to her friends and whether or not they were inside when the shooting occurred.
"I was really worried for my friends that were coming in. We were trying to stay calm but it was really scary," she said. "We're just really shaken."
All of Newman's friends were accounted for and were not among the injured.
Virginia Governor Terry McAuliffe said he had spoken to the mayor of Richmond and the state police superintendent and was 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 in a statement.
Virginia Attorney General Mark Herring said the situation was "heartbreaking and frightening" in a post on his Twitter account.
Richmond City Councilwoman Reva Trammell told WWBT "I would never believe this."
"This is one of the saddest days that I've seen in the city of Richmond," she said.
Dermyer was a former Marine and had been a member of the Virginia State Police since 2014, Flaherty said. He had recently been transferred to the department's counter-terrorism unit.
"He was a great trooper," Flaherty said.
Dermyer is survived by his wife Michelle, and two young children, officials said.