The victim was leaving the Chase Bank in the 500 block of North Euclid Street at about 4:15 p.m. when she was suddenly beaten in the parking lot.
"Our investigation determined that she had tried to rob the victim and actually assaulted her by hitting her in the head with a hammer," said Sgt. Mark Irwin with the Anaheim Police Department. "It is apparently a crime committed by a complete stranger."
Bank employees and customers managed to detain the suspect until police arrived. She was taken into custody.
The victim was taken to UC Irvine Medical Center with injuries to her head and face.