DANVILLE — An 83-year-old San Ramon man will not face charges in connection with two separate hit-and-run accidents along Diablo Road in October that left three bicyclists injured, two of them seriously.

Sophea Nop, a Contra Costa County deputy district attorney, said late Wednesday that she declined to file charges against Daniel Brennan after determining “that we could not prove the charges beyond a reasonable doubt.” She said she had no further comment.

Brennan was arrested Oct. 23, two days after the accidents, on suspicion of three counts of felony hit-and-run, and was released pending further investigation.

Police said Brennan was driving west on Diablo Road about 1:20 p.m. Oct. 21 when the 2006 Ford Escape he was driving struck a woman bicyclist, also headed west on Diablo Road, near Avenida Nueva. She was not seriously injured.

About 40 minutes later, the same vehicle — this time headed east on Diablo Road — is believed to have hit two bicyclists headed east on Diablo Road near Clydesdale Drive. Those bicyclists, both men, were seriously injured; one suffered spinal fractures and the other suffered a broken arm and head injuries.

Danville police found the Ford Escape at a relative’s house during a canvas of the Hidden Oaks at Blackhawk neighborhood.