A member of her PPP party, Mohammad Zaman, told the BBC what happened next:
"The meeting went perfectly well. She delivered her speech, she came down the stage and got on the land-cruiser.
"She started coming out, we heard three [shots] fired, and after that the bomb blast went [off].
"And when I came down the road I saw there was loads and loads of injured. And I really thought that her vehicle was safe and left the place safely. I was hoping she would be OK."
A BBC correspondent at the rally, Shahzad Malik, said Ms Bhutto had got out of her car to wave to a group of supporters who were chanting slogans in her support near the main gate of the park where the rally had been held.
It was then that the bomber struck.
"I heard a blast. I rushed across to where so many people were lying injured and dead," our correspondent said.
Police officer Mohammed Shahid gave this account: "The man first fired at Bhutto's vehicle. She ducked and then he blew himself up."
Ms Bhutto was taken to hospital. But emergency surgeons failed to save her life.
Officials say Ms Bhutto was shot in the neck, but it is not clear if the shots, the blast, or a combination killed her.
Crying and hugging
There were emotional scenes outside the hospital, with some people crying and hugging each other, and others shouting "Dog, Musharraf, dog" - a reference to the Pakistani president.
The BBC's Haroon Rashid reported from outside the hospital that hundreds of her party workers were still gathered there hours after her death was announced.
He said that others were coming from inside the building urging them to go on the rampage to show their feelings.
"What good are you doing standing around here?" they were asking.
Not long afterwards, lights went out and no police were in view. Our correspondent says getting Ms Bhutto's body out of the hospital for her funeral will present a huge logistical challenge.
Mobs and fires
As news of the death spread, reports emerged of protests breaking out around Pakistan.
As well as trouble in Rawalpindi itself, where Bhutto supporters burned election posters belonging to the ruling party, there were demonstrations in the north-western border city of Peshawar, and in Karachi, where shopkeepers closed their businesses as thousands of people poured out onto the streets.
The unrest was most fierce in Ms Bhutto's home province, Sindh, and security forces were on red alert there, as in the rest of Pakistan.