The body of Deputy Marshal Vincent Bustamante was found with multiple gun wounds to the back of his head, according to Chihuahua state police.
The officer had been been the subject of an arrest warrant accusing him of criminal theft of US government property, CNN reported. The network was told by a federal law enforcement source that the marshal had been stealing the property and then pawning it.
His alleged activities came to light after a pawnshop owner became suspicious when Mr Bustamente attempted to pawn a shotgun. He was put on “modified status” duty during the investigation, meaning he had been required to turn in his gun and badge outside of his official work hours.
It was not immediately clear why he had been in Juarez or whether his killing was linked to his alleged criminal activity.
More than 6,000 people were killed last year in drug violence in Mexico as rival narcotics cartels battled with each other and with the thousands of federal troops deployed by President Felipe Calderon. The worst violence was concentrated on key smuggling transit cities along the US border.
The news of Marshal Bustamente’s murder came on the same day that Hillary Clinton, the US Secretary of State, watched police storm an airplane in a mock hostage rescue at the end of a two-day visit to Mexico.
Mrs Clinton has discussed the “intolerable” drugs violence during her visit. But she also said that the demand for drugs from the US and weapons smuggled south across the border were a major contribution to the bloody mayhem.