An Oregon man is facing murder and sodomy charges after police said he killed his girlfriend's toddler daughter.

According to the Mail Tribune, Jackson County deputies arrested Russel Brian Darrel Larsen, 25, on Aug. 15, 10 days after 2-year-old Alivia Rose Allen died from blunt-force trauma, authorities said.

Investigators said Larsen had been watching the child Aug. 5 at his girlfriend's Eagle Point home, where he had recently moved, the Jackson County Sheriff's Office said in a news release. The girl's mother later discovered that the toddler wasn't breathing and called 911, authorities said.

Alivia later died at Asante Rogue Regional Medical Center, the news release said.

On Aug. 8, an autopsy determined that the girl had died in a homicide, officials said. The following week, authorities charged Larsen with first-degree manslaughter, assault and criminal mistreatment, according to the Sheriff's Office.

This week, those charges were upgraded to include murder and first-degree sodomy, the Mail Tribune reported. Investigators believe that Larsen caused the girl's death "while committing or attempting to commit sodomy," according to the newspaper.

Larsen, whose bail was originally set at $207,500, is now jailed on $1 million bond, officials said.

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