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LONGMONT, Colo. (KDVR) — A woman accused of killing her ex, a Longmont postal worker, has been found guilty of first-degree murder.

Investigators have said Devan Schreiner was the ex-girlfriend of victim 33-year-old Jason Schaefer, a mail carrier who was shot and killed in the Somerset Meadows neighborhood. A Boulder County jury delivered the verdict on Tuesday.

“This defendant is a cold-blooded murderer,” 20th Judicial District Attorney Michael Dougherty said in a statement.

Dougherty said Schreiner “took steps” to get away with the murder, but the information provided by Schaefer’s family and co-workers “was critical” in the investigation.

The U.S. Postal Inspection Service and the Longmont Police Department investigated the case.

Court records from the time of the killing show a battle had been brewing between Schreiner and Schaefer.

The two had worked together at the Longmont post office, but Schreiner was fired two weeks before and began working as a mail carrier in Loveland.

“Jason had filed documents to have parenting time modified” two days before the shooting, according to an arrest affidavit.

“Devan was supposed to be served with the papers,” the affidavit reads, with investigators saying they were told Schreiner had threatened Schaefer.

She was on duty the day of the shooting, but her mail truck was not moved for hours.