CLARKSVILLE, Tenn. -- Clarksville and Metro police are investigating the alleged sexual assault of a taxi driver by a Fort Campbell soldier.

Police: Soldier Kidnapped, Assaulted Taxi Driver

Police believe a female driver picked up 18-year-old Gregg Walter Johnston and stopped at a couple places Saturday morning in Clarksville.

Johnston said he didn't have cab fare, so a stop was made at Durrett Village Apartments for him to get money from a friend. Police said he then made the taxi driver drive to Nashville at gunpoint, where he allegedly assaulted her.

The Fort Campbell soldier then allegedly forced the woman to drive him to Oak Grove, Ky., where he got out at a Walmart and ran away. His whereabouts are unknown.

The taxi ride, police said, lasted four-and-a-half hours.

"You never really think that it's going to happen to one of your own," said Daryl Brewer, a co-worker of the woman.

Police said Johnston has a Fort Campbell address.

An aggravated kidnapping warrant for Johnston was issued Wednesday.

Reporter Carley Gordon contributed to this story.