Terry Sayachak, 28, threatened his father with a gun in the 4400 block of Z Street around 6:15 p.m. Monday, then drove away with his girlfriend in a Toyota Camry, San Diego police homicide Lt. Kevin Rooney said.
He later returned to the scene around 7 p.m. but drove off when he spotted officers taking a report, according to San Diego police Sgt. David Jennings.
Minutes later, he ditched the Camry and carjacked a Mitsubishi Gallant that was stopped at a red light at National Avenue and 45rd Street, Rooney said.
He ordered the Gallant's owner to drive but took the wheel after the owner jumped out of the car, Rooney said.
The man continued on in the carjacked Gallant, with officers in pursuit, until he crashed into several parked cars in the 800 block of 46th Street, according to Rooney.
He suffered critical injuries and was taken to an area hospital, where he remained this morning, according to Rooney.
Officers found the abandoned Camry with the man's dead girlfriend inside at around 10:15 p.m. in the 500 block of Elizabeth Street. Her name was not immediately released.
The apparent cause of death was a gunshot, Rooney said.