Ferrebee was charged with driving under the influence, and Brown, a passenger, was charged with being drunk in public, the release said. Ferrebee also faces a charge of possession of a weapon by a convicted felon, the release said.
As the damaged truck was being moved, a firearm inside it went off and Trooper Kevin C. Manion was shot in the chest, the release said.
The bullet entered Manion's side near one of his arms in an area not covered by the bulletproof vest he was wearing, Virginia State Police spokeswoman Corinne Geller said. The bullet traveled to Manion's chest, Geller said.
The trooper died later Saturday afternoon, the release said.
Geller said Monday that investigators were trying to determine how the gun went off.
Geller could not comment on where the gun was in the truck, adding that state police are being careful about commenting further because it is "such an unusual incident."
Geller did say that the gun that discharged was not Manion's weapon.
The accident occurred about four miles north of Va. 17/50, police said. The site is about 20 miles south of Charles Town, said Sgt. F.L. Tyler of the Virginia State Police.
Manion, 27, joined the Virginia State Police in October 2002 and graduated June 6, 2003, as a member of the 104th Basic Session, according to a state police release.
Manion earned a bachelor's degree in geography from Mary Washington College in Fredericksburg, Va., and an associate degree in education from Dabney S. Lancaster Community College in Clifton Forge, Va., the release said.
"This is a tremendous loss shared by every member of our department. Our hearts and prayers are with the Manion family as they come to terms with the devastating loss of a beloved son and brother," Virginia State Police Superintendent Col. W. Steven Flaherty said.
The Northern Virginia Daily contributed to this story.