A 19-year-old Illinois man pleaded guilty to killing his girlfriend in 2024 and staging the murder to look like a suicide.

As part of the plea agreement, Nathaniel N. Archuleta was sentenced to 45 years in prison without the possibility of parole, the Peoria County State’s Attorney’s Office announced.

Archuleta admitted to first degree murder in the case of 20-year-old Mary Halcomb on September 6. On that day, police responded to a report of a woman who had allegedly shot herself and found Halcomb in a pool of blood on a stairwell landing with a gun in her hand.

She was pronounced dead on the scene from a single gunshot to the neck.

However, as detectives continued their investigation, they discovered inconsistencies suggesting that things were not as they appeared. Among their findings was a blood trail leading from a downstairs bedroom to the landing where the body was located, indicating that the body might have been moved. In that bedroom, they discovered a post-it note stating: “I, Mary Elyce Halcomb, promise to never break Nathanial Archuleta’s heart, and if I do, Nathaniel Archuleta has every right to euthanize me, vice versa, I love you.”

For his part, Archuleta gave conflicting accounts of what happened. He first said it was a suicide, then said he was trying to clean his gun when it “accidentally” went off.

Later, detectives learned that Archuleta admitted to another inmate that he had killed Halcomb because he caught her texting another man.

Halcomb’s family members spoke at the hearing this week, telling the court of their experiences since Halcomb’s death.

“They spoke of sleepless nights, nightmares, and persistent heartbreak. They described their overwhelming sense of loss, loss of sisterly moments, shared dreams, and life milestones that will never come,” the state’s attorney’s office said. “Mary’s loved ones described struggling with trust, fear, depression, and anxiety. They called Archuleta’s actions selfish and unforgivable, stating that blood will forever be on his hands and that justice must now be served.”