An arrest has been made in the case of a Louisiana letter carrier who was shot and killed while bringing mail to the home of his assailant, but the motive – if there was one – remains a mystery.

News reports say 32-year-old Michael Gentry was arrested in the incident, which occurred in Shreveport. Gentry allegedly shot 52-year-old Antonio Williams while Williams was doing his job. Williams was taken to a nearby hospital where he died a short time later.

Authorities said they have uncovered no evidence of a dispute between the two men prior to the shooting.

Gentry is being held in the city jail on one count of second degree murder, with a bond set at $250,000.

Shreveport police said the U.S. Postal Inspection Service; the Bureau of Alcohol, Tobacco, Firearms, and Explosives; the FBI; and the Drug Enforcement Administration were involved in the investigation.