Police Cmdr. Pat Gannon told reporters the brawl ended Monday afternoon when one of the women got into a gold convertible and drove into the crowd, the Los Angeles Times reported Tuesday.
"It was totally an intentional act to kill the woman. It was the driver's way of settling the dispute. It was a horrific act," said Deputy Chief Charlie Beck.
A witness who asked not to be identified told the Times the driver hit the pregnant woman with the car, dragged her several feet until she fell off, then backed up and ran over her again.
Of the two other women injured, one was in critical condition and likely to lose a leg, police said.
While Gannon said the cause of the apparently planned dispute was unclear, the witness said it was over a man, the Times reported.
The driver initially fled the scene, but later stopped at a police station where Gannon said she claimed it had been an accident, the newspaper said.