The bear was shot Aug. 3 and is believed to have died 12 days later, the Anchorage (Alaska) Daily News reported.
A guard working for Purcell Security, a BP contractor at the Endicott oil field, believed he had fired a bean bag at the bear, Steve Rinehart, a BP spokesman said. The bean bag, fired from a 12-guage shotgun, was intended to annoy the bear, which was approaching employee housing, and encourage it to move on.
But the U.S. Fish and Wildlife Service discovered during a necropsy Aug. 16 the bear had been struck by a projectile. The guard fired a noisemaker that hit the bear, causing internal injuries.
The bear was spotted several times in the area before its death.
A spokesman for Fish and Wildlife said the death was under investigation.