The man called base officials from a pay phone and apparently left the guns behind a horse trailer at the stables on the west side of the installation.

A letter of apology was left with the weapons. The caller, who did not identify himself, may still face charges if he is found.

It is unclear what the person who took the box of 12 guns intended to do with them. The box was taken after it fell from the vehicle at about 3:45 p.m. Tuesday. The guns are worth up to $5,000 each on the black market. According to base officials, the 729th Air Control Squadron lost the rifles.

Several witnesses said they saw a green box in the road and several others claimed to have seen a middle-aged, heavyset white male, of medium height with gray hair and wearing civilian clothes, lifting it into a car.

Hill has been embroiled in a chain of mishaps and scandals recently, including a friendly fire incident at the Utah Test and Training Range, the accidental burning of radioactive materials at a civilian incinerator and the mistaken transfer of nuclear-missile parts to Taiwan. The latter debacle sparked an investigation that led to the resignation Thursday of the Air Force's top two officials.

In the case of the missing machine guns, Air Base Wing Security Commander Shannon Smith said the unit that lost the weapons was returning from field exercises and had loaded the container onto the flatbed back of a Humvee, but failed to secure the case, which apparently fell out of the vehicle just south of the base's Roy Gate.

By the time the unit's airmen arrived at their destination and realized the weapons were missing, several commuters had reported to base security seeing a green box in the road. But by the time the unit's security personnel returned to where the weapons had fallen, the box was gone.

Smith said it might have taken up to an hour before all base gates were shut down and checks were being performed on all cars leaving the base. He also said the person who picked up the weapons easily could have taken them off the base even before security knew what was in the box.

mlaplante@sltrib.com