Celebrities and millions of fans mourned the death of Lucille Ball, the carrot-topped comedian who was one of television's most original and enduring stars.

The city of Los Angeles paid tribute to Ball Thursday by ordering flags flown at half-staff.Ball, 77, beloved by generations of television viewers, died of a ruptured aorta Wednesday, eight days after undergoing emergency open-heart surgery.

Hours after she died, flags at City Hall, municipal courthouses and police stations were ordered lowered until the day of her funeral. Arrangements were pending.

"Oh, what a blow," comic actor Dick Van Dyke said after learning of Ball's death. "What a shame. Damn. She didn't deal in jokes, she dealt in human behavior."

It was just one of hundreds of expressions of shock and sorrow at the loss of one of the world's funniest and most savvy women - the inventor of the situation comedy and the rerun.

Her doctors and family were stunned. She had been walking around her hospital room and eating, and they had issued optimistic predictions that Ball would be able to resume her career.

Ball's husband, Gary Morton, and her two children, Lucie Arnaz and Desi Arnaz Jr., were in "deep grief and shock and not accepting any calls," a family spokesman said.

"It was totally unexpected," said Ron Wise, a spokesman for Cedars-Sinai Medical Center. "There was nothing in the previous week that would have indicated this at all."

Ball's heart surgeons, Drs. Robert Kass and Auerlio Chaux, said a section of her aorta - the heart's main artery - burst about 5 a.m. and so much blood escaped that none was left to pump through her heart.

"You are asking yourselves `was it possible to do something else to try to save her?' and the answer to that is `no,' " said Chaux. "The chances of somebody recovering from that second episode are very, very small, if not zero."

President Bush extended his "deepest sympathy" to Ball's family, and called her a "legendary figure." "We too loved lucy. So did the world."