Los Angeles, California (CNN) -- Longtime Hollywood publicist Ronni Chasen was gunned down on Sunset Boulevard early Tuesday, just minutes after she left a star-studded party to celebrate the premiere of the movie "Burlesque," police said.
"We were all on such a high," songwriter Diane Warren said. "And then she left -- I'm guessing about 10 minutes before I did. What on earth? What happened? Why?"
Chasen, 64, died when "multiple shots" were fired into her Mercedes seconds after she drove past the posh Beverly Hills Hotel on her way home, according to Beverly Hill Police Sgt. Lincoln Hoshino.
Police found her car crashed into a light pole after responding to a report of gunfire heard near the intersection of Sunset and Whittier Drive at 12:20 a.m. (3:20 a.m. ET), Police Sgt. Robert Maycott said.
Chasen died later at Cedars-Sinai Hospital, according to Lt. Fred Corral, a spokesman for the Los Angeles County coroner.
Detectives searched Chasen's West Los Angeles home and her public relations firm for clues Tuesday, but Hoshino called it "a wide open investigation." They have no suspects or motive for the attack, he said.
Warren, who was Chasen's celebrity client, called the killing senseless.
"They didn't steal anything," she said. "Her purse was still there."
Chasen had been on the red carpet at Grauman's Chinese Theatre walking with Warren as she and "Burlesque" star Cher were interviewed about the music in the film.
Warren, who contributed a song to the movie's soundtrack, said Chasen also went with her to the after-party at Hollywood's W Hotel.
"I am devastated beyond belief," Warren said. "I can't believe this. I can't believe this."
Michael Levine, head of Levine Communications Office, called Chasen a "beloved, iconic figure."
Levine, who said he has known Chasen for 25 years, has started a reward fund with a goal of raising $25,000 by next week.
"We must do everything possible to assist the Beverly Hills police in solving this horrific crime," Levine said. "Ronni gave the utmost for her clients and this industry."
Hollywood celebrity public relations is "like a small family," said Edward Lozzi, who operates a small Beverly Hills firm.
Chasen was a "class act" and "the ultimate professional," Lozzi said.
Chasen was "so good promoting great films," and had special talent for creating pre-Oscar buzz for her acting clients, publicist Steve Jaffe said.
CNN's Denise Quan and David Daniel contributed to this report.