A Mills man faces a lengthy prison stay after admitting his role in a March stabbing in Casper.

Thirty year old Robert Simmons was sentenced to 20-to-25 years in prison, after pleading guilty to one charge of aggravated burglary.

At the same time, he will also serve an eight-to-10 prison sentence for aggravated assault.

According to investigators, Simmons was with Zacharia Johnson in early March, when they entered the home of Robert Masterson and stabbed him several times.

When interviewed by police, Simmons admitted to stabbing Masterson once.

Two days after the stabbing, Simmons crashed his car into the North Platte River in Mills.

While checking Simmons for injuries, police confiscated a knife.

Detectives were later informed by fire personnel at the hospital, that Simmons told them something to the effect that he was trying to “atone for his sins for stabbing a guy the other night,” and that was the reason he drove his car into the river.

Prosecutors noted that Simmons has an lengthy criminal history.

Meanwhile, Johnson is facing charges of attempted first degree murder, related to the case, and is awaiting trial.