The alleged robbery was caught on Paul Liao’s dash cam video and is being investigated by Los Angeles County Sheriff’s Department.
Investigators are still determining if it was a racially-motivated attack and Mr Liao, 67, says his assailant asked him about his ethnicity.
“I was very scared,” Mr Liao told KCAL-TV.
“Two choices, he want the car and he want the money, that’s it,” he added,
Authorities say the suspect got into the back seat of Mr Liao’s car as he filled it up at a gas station in the suburb of El Monte as he waited for his next ride.
The dashcam video shows Mr Liao being hit several times with a pistol, leaving him with a bloody nose.
The suspect demanded his wallet and cell phone and allegedly took $1,500 in cash.
He fled the scene when Mr Liao told him his car was keyless and he would not be able to drive it if he tried to take it.
“I said my car is a new system, it doesn’t have a key, you cannot drive it, you cannot move,” said Liao.
Investigators say they already have received a number of tips on the attacker’s identity.
“We’re using many new systems at our disposal through the sheriff’s department to help identify this individual and we are very confident we will have the individual in custody soon,” said Los Angeles County Sheriff’s Sergeant Richard Lewis.