Authorities responded to a 911 call on the 800 block of North Whittier Drive, near Sunset Boulevard, just before 12:30 a.m. Residents in the area had reported hearing several gunshots fired.
Moments later, a second 911 call reported a solo car crash.
Police said Chasen was shot several times in the chest while sitting inside a newer Mercedes-Benz 350 series. It appeared she was the driver of the car and her injuries caused her to crash.
Chasen was rushed to Cedars Sinai hospital, where she was pronounced dead.
Just hours before she died she had attended the premier for the film, "Burlesque," which she was promoting. She had promoted such major motion pictures as "Slumdog Millionaire," "Driving Miss Daisy" and "On Golden Pond" during her long career.
Industry leaders expressed their sadness and shock at Chasen's death.
Paul Bloch, co-chairman of Rogers and Cowan, released a statement: "She was a powerhouse in the industry. She was as good as it gets. She was a great woman and a brilliant publicist. I have known her for over 30 years. She had a great personality."
Roger Ebert tweeted, "Oh, no. Publicist Ronni Chasen shot dead. She was a friend."
Publicist and friend, Elaine Ross, called her the Elizabeth Taylor of public relations. "Everybody knew her. Especially people that were directors, and writers, and composers and stars." Fellow publicist Michael Levine said he is establishing a reward fund for information that leads to the capture and conviction of Chasen's killer.
Beverly Hills Police Lt. Tony Lee said the shooting was unusual.
"We don't have crimes like this in the city of Beverly Hills, so it is a surprise to us," said Lee.
A motive has not been determined, and the shooting remains under investigation. There were no visible damages from bullets inside Chasen's car. Investigators have seized computers from Chasen's business.
Lee said because police have little information to work with, they could use the public's help. Anyone with information related to the incident is urged to call the Beverly Hills Detectives Hotline at (310) 288-2656.
The Associated Press contributed to this story
