A man who is already serving a prison sentence in the Wyoming State Penitentiary was sentenced to spend about another decade behind bars for the sexual assault of a young girl.

Brian Christopher Bass, 25, was sentenced Wednesday before Natrona County District Court Judge Daniel Forgey to serve 12-15 years in prison after pleading guilty in January to two counts of second-degree sexual abuse of a minor.

Bass is currently serving a four- to six-year prison sentence for marijuana distribution. He told Forgey he has roughly two years to serve on that sentence before he would be eligible for parole.

Forgey cited "aggravating circumstances" -- including prior criminal history and the fact that Bass was on probation at the time of the sexual assault -- in his decision to order the 12- to 15-year sentence run consecutively to the sentence Bass is already serving.

Assistant District Attorney Brett Johnson said Bass displayed "breathtaking arrogance and selfishness" in the case, explaining the victim experienced the "worst pain she's ever felt in her life," but Bass continued anyway.

"She'll never be the same," Johnson told the court, adding that the only reason the crime was not charged as first-degree sexual assault of a minor was the victim didn't say 'no.'

Court documents say Bass and the victim met through a smartphone app called "Whisper." The two began speaking sexually and, when Bass said he was in his 20s and the victim gave her age, Bass said it "didn't matter about age."

On Aug. 13, Bass picked the victim up in a black pickup and took her to a construction site, where he had sex with her.

A relative of the victim spoke in court Wednesday on the victim's behalf, after the victim -- who had wanted to speak herself -- became emotionally distressed and could not attend the hearing, the relative said.

"She has made a lot of strides in the last six or seven months," the relative said of the victim. "It's just been a very great trial."

The girl's grades have slipped from As and Bs to Cs and Ds since the assault, the relative said. She now deals with anger issues and has to take "mental health days."

"It's been tough on our family," the relative said.

Bass was also ordered to pay $3,006.40 in restitution.