SALT LAKE CITY (AP) – A Colorado man who pleaded guilty to killing his Utah girlfriend with a shovel over a mistaken pregnancy when he was 14 was sentenced to prison Monday.

Darwin “Christopher” Bagshaw, 18, was sentenced to at least 15 years behind bars.

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The judge called the beating unspeakably vicious and cruel as he handed down the punishment in Salt Lake City.

The night of her death, 15-year-old Anne Kasprzak told him she was pregnant and they had to run away together, authorities said. Bagshaw was angry and hit her in the face several times with the shovel, his defense attorney acknowledged. Her body was found floating in the Jordan River. An exam found she wasn’t pregnant, and her family later said she made up the story.

The girl had survived an abusive childhood, going through several foster homes before she was adopted by the Kasprzaks at age 9, her parents said. She’d just begun to come into her own when she was killed by a boy from her math class who she really liked, said mother Veronica Kasprzak, reading from her daughter’s journal.

“Her only mistake was falling in love with the hope of a future with you,” Veronica Kasprzak said. “You took her away from us because you thought she would complicate your life.”

Bagshaw’s lawyers said he was scared and angry and was too young to process what was happening that night.

Darwin

Darwin “Christopher” Bagshaw (credit: Salt Lake County Sheriff’s Office)

“Darwin needs to be punished, but he needs to be punished at the level of a 14-year-old and not like an adult,” said attorney Christopher Bown.

Bagshaw said he had severe anxiety when he stepped up to speak Monday. He apologized to the victim’s family and his own.

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Judge James Blanch refused a last-ditch effort to reduce his sentence, saying he was bound by state law and not inclined to find that the 15-year minimum was too harsh.

“Words fail when one imposes sentencing in a case like this,” Blanch said. Under Utah law, Bagshaw could serve up to life in prison. A parole board will set his eventual release date.

Kasprzak was killed 2012, but the investigation was delayed when police arrested two ex-convicts on a fake tip. After they were cleared, police circled back to Bagshaw, who had moved to Grand Junction, Colorado, with his family.

While defense lawyers said his relatively normal teenage life in the more-than two years between the girl’s death and his arrest showed he wasn’t likely to be violent again, the victim’s family said he prolonged their grief by not coming forward sooner and should serve the full sentence.

“I’m sorry, but culpability at 14 is there. Right or wrong, it’s there,” said her father, Dennis Kasprzak.

Bagshaw was originally charged as a juvenile, but a judge certified him to stand trial as an adult. He made the decision to take responsibility and plead guilty about a week before his trial was supposed to begin, his lawyers said.

Prosecutors said that Bagshaw confessed the crime to a fellow inmate at a juvenile detention center, and the teen reported it. While the defense calls that account overblown, prosecutors say that without the new evidence Bagshaw might not have pleaded guilty.

“Her last moments were spent pleading for her life on that riverbank,” said prosecutor Peter Leavitt.

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