The car jumped the sidewalk and drove through an area under a bridge with a number of tents, according to officials.
A total of nine victims were struck, police said. Two are in critical condition but are awake, alert and answering questions, police said.
The 71-year-old driver, Craig Voss, was detained for allegedly driving while impaired and charged with three counts of vehicular manslaughter, five counts of causing great bodily injury while committing a felony and one count of felony DUI, police said.
Voss was rendering aid to a victim when officers arrived, police said.
The incident occurred near San Diego City College, ABC San Diego affiliate KGTV reported.
Multiple ambulances were sent to the scene.
ABC News’ Matthew Furhman and Alex Stone contributed to this report.