Bhutto was rushed to a nearby hospital while rescue workers hurried to put victims in ambulances as people wailed nearby. The clothing of some of the victims was shredded and people put party flags over their bodies. Police caps and shoes littered the asphalt.
In the confusion, it wasn't clear exactly what had happened, but Sardar Qamar Hayyat, a leader from Bhutto's party, said he was standing about 10 yard from Bhutto's vehicle.
"She was inside the vehicle and was coming out from the gate after addressing the rally when some of the youths started chanting slogans in her favor," he said. "Then I saw a thin, young man jumping to her vehicle from the back and opening fire. Moments later, I saw her speeding vehicle going away."
Party supporter Chaudry Mohammed Nazir said that two gunshots rang out when Bhutto's vehicle pulled into the main street and that there was a big blast next to her car.
A security adviser to Bhutto's party said she was shot in the neck and chest.
The gunman then blew himself up.
Initial reports said Bhutto, 54, was unharmed in the attack, but about an hour later her supporters' worst fears were confirmed.
Sen. Babar Awan, Bhutto's lawyer, said, "The surgeons confirmed that she has been martyred."
There was no immediate claim of responsibility for the killing, but at Rawalpindi General Hospital furious Bhutto supporters erupted in anger at Pakistan's president, Pervez Musharraf, chanting "Killer, Killer, Musharraf" and calling him a "liar."
The Pakistani military was in charge of security at the rally and it was the second time since Bhutto returned to Pakistan in October that an assassin slipped past security.
During her triumphant return to the country, Oct. 18, a suicide bomber blew himself up near Bhutto's vehicle, killing more than 140 people. Bhutto survived that attack.
"We repeatedly informed the government to provide her proper security and appropriate equipment including jammers, but they paid no heed to our requests," said Rehman Malik, Bhutto's security adviser.
Last month, Bhutto had also planned a rally in the city, but Musharraf forced her to cancel it, citing security fears.
Pakistan's Islamic militants have long had Bhutto under a death sentence for her opposition to their fundamentalist ambitions. There were also tensions between Bhutto and Musharraf after negotiations to share power had stalled.
In his televised address to the nation, Musharraf blamed his rival's death on terrorists and vowed, "we will not rest until we eliminate these terrorists and root them out."
But Sharif, another former premier who was deposed by Musharraf, rushed to the hospital where Bhutto had died and in an address to the crowd suggested the Musharraf government was at fault.
"Benazir Bhutto was also my sister, and I will be with you to take the revenge for her death," Sharif said. "Don't feel alone. I am with you. We will take the revenge on the rulers."
Today's attack took place as Bhutto was leaving a political rally where she addressed thousands before the country's Jan. 8 parliamentary elections.
The killing has staggered Pakistan. Musharraf had put Pakistan under emergency rule last month and postponed elections. Under pressure from the White House, Musharraf rescheduled the elections for January and lifted emergency rule.