The owners of the ranch, Michael and Marianne Rountree, have put forward $5,000 and donations from the public have brought the reward to a total of $17,000.
"The detective believes it's someone in the area that is either a teenager or in their 20s that is familiar with the area," said Greg Rountree, another owner, adding that teenagers from Danville are known to party on Collier Canyon and Highland Road.
He also noted that a cow was shot on Manning Road and the horses were shot on Collier Canyon that evening with the same .223 rifle. He said authorities believe the crime occurred at 9:30 p.m. Tuesday night based on a witness that heard three shots and the autopsy report from UC Davis.
The two horses, named Choctaw and Lucky, worked on the Rountree's Collier Canyon Road ranch with sick and developmentally disabled children.
"One of the horses was a show horse that has been seen by millions of people on TV in parades like the Rose Parade, and frequently visited children at the Shriner Hospitals and Adaptive Local Riding Centers," Rountree said. "The other horse we rescued in March from the SPCA and had just been nurtured back to health. He was shot twice in the stomach and died after he had walked 1/4 mile trying to get back to the barn."
He said publicity generated a call from Canada with an offer to ship a horse to the Rountrees.
"It is tragic and frightening that someone would have such disregard for life," said East Bay SPCA Operation Director Amelia Funghi. "That disregard caused two innocent and beautiful animals needless suffering and the loss of their lives."
Rountree said investigators would like to talk to the owner of a white Acura TSX model sedan, year range narrowed down to 2004-2007 model, with a loud muffler that crashed in to a barbwire fence on Manning Road that evening around 9:30 p.m. The car will be scratched from fence and have a broken taillight.
Anyone with information about the incident is asked to call Scott Sutherland with the Contra Costa County Sheriff's Department at 313-2654, or the Alameda County Sheriff's Department at (510) 667-7721.
--Janet Pelletier, Dolores Fox Ciardelli