At about 10:15 p.m. Pleasanton police responded to a report of an assault at 3821 Vine St., the home of the grandmother, Paula Thurman.
A man had reportedly knocked on her front door, said he was with the Sheriff's office, asked Thurman about her family and then punched her when she tried to respond, according to the Pleasanton Police Department.
Thurman reportedly screamed and the man ran away, police said. Thurman was taken to Eden Hospital where she is recovering from injuries.
The suspect was described only as a white male with brown hair, 30 to 40-years-old, about 5 feet 7 inches tall and weighing 160 to 180 pounds. He was wearing a white tank top and jeans.
Police are still searching for the suspect and investigating the situation. Anyone with information is asked to call the Pleasanton Police Department at (925) 931-5100