An Illinois man is headed to prison for murdering his girlfriend and then trying to make it look like she died by suicide by planting a note.

Nathaniel N. Archuleta, 19, was sentenced Monday to 45 years in prison after he pleaded guilty to first-degree murder in the death of 20-year-old Mary Halcomb in South Peoria, the Peoria County State Attorney”s Office said in a press release.

Cops responded on Sept. 6 to a home in the 1400 block of South Griswold to calls of a woman who shot herself. Officers entered the home and found Halcomb in a pool of blood on the stairwell landing suffering from a gunshot wound to the neck. She held a gun in her hand. First responders pronounced her dead.

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During their investigation, cops discovered some writing that purported to offer an explanation.

“In the downstairs bedroom was a post-it note that read, ‘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,'” the county attorney’s office said in the press release.

But detectives discovered evidence that was inconsistent with a suicide — specifically a blood trail from the bedroom to the landing area, which suggested that Halcomb’s body had been moved.

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Archuleta gave “conflicting accounts” of what happened on the night in question, first insisting it was a suicide and then claiming he was cleaning his gun and it accidentally went off. But he later told a fellow inmate he shot his girlfriend because he “caught her texting another man,” prosecutors said.

Prosecutors stated Monday’s plea hearing was filled with Halcomb’s family members who described the emotional toll her death has taken.

“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 press release 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.”