Authorities are seeking a gunman who has killed at least four Thoroughbreds in their pastures with a small caliber rifle near Fresno, Calif., in the past week.The California Thoroughbred Breeders Association has offered a $5,000 reward to anyone with information regarding whoever is responsible for the shootings.Three farms in Sanger, including Old English Rancho and one owned by longtime trainer Elmer January, reported shooting incidents between March 10 and 12. Sanger is located 15 miles east of Fresno. A fourth farm owner in the immediate area made an additional report March 15 on another horse's shooting death, a Fresno County Sheriff's investigator said, but details were unclear. If confirmed, that would bring the total of dead horses to at least six. Old English farm manager Craig Allen confirmed that two yearling colts, both owned by the ranch, were shot to death by "some freak taking potshots at animals in our area" March 12. The shooting took place at about 4:30 p.m. (PST) as the colts grazed in a pasture with 15 other yearlings near Piedra Road, which fronts the ranch. Allen said they were fired upon at a distance of 30 to 40 feet. A third yearling was hit, probably by a ricocheted slug, he said, but was not seriously injured. A .22 caliber round was retrieved from one of the dead animals. Allen declined to give the parentage of the deceased yearlings at this time, citing client security concerns. The 78-year-old January, who is a neighbor of Old English Rancho, said both of his horses -- unbroken 3-year-old Thoroughbred fillies -- were found dead near his fence line next to Piedra Road the day before the Old English shootings. He said he was not sure of the cause of death at the time and did not initially file a report with the sheriff's office. But after learning of his neighbor's misfortune, he had a veterinarian check for bullet holes."They were shot," confirmed January, who has 60 head on his ranch. "It worries you. I've got a pasture full of them (horses) now. I've been here 44 years and nothing like this has ever happened before."In a third incident, which occurred March 10 at 6:30 p.m., a 6-year-old Paint was shot in the right rib cage area. The unidentified owner of the farm heard a gunshot, saw a vehicle pull in front of his residence and heard a second shot. He ran outside to check his horses and saw what he said was a minivan fleeing the scene, according to the sheriff's department.The day after the shootings at Old English Rancho, a maintenance worker at the ranch said he heard four popping noises, which he thought were possibly gun shots, east of his residence. He observed a brown or dark colored Ford Windstar minivan of recent make traveling south on Piedra Road.Authorities believe the shootings are random crimes and that the farms were not targeted by the killer.