Q&A: Benazir Bhutto assassination

Benazir Bhutto poses for a photograph on the Pakistani Peoples Party bus on her welcome home parade on October 18, 2007

Benazir Bhutto, twice prime minister of Pakistan, was assassinated on 27 December 2007, while campaigning for parliamentary and provincial elections.

How did it happen?

Ms Bhutto was attacked as she was leaving a rally of her Pakistan People's Party (PPP) supporters in the garrison town of Rawalpindi.

She was standing upright in the her armoured vehicle, with her head exposed above the open roof escape hatch, waving to the crowd when an attacker opened fire.

Seconds later, a bomb was set off at the scene which left some 20 other people dead.

The exact cause of Ms Bhutto's death is disputed.

UK police were asked by the Pakistani government to investigate the killing. They concluded she was killed as a result of the explosion.

Ms Bhutto's party has insisted it was the gunshots that killed her. They say they saw bullet wounds on her head while preparing her body for burial.

The British police report released on 8 February said the impact of the explosion forced Ms Bhutto's head to collide violently against the side of the escape hatch.

The report also said the attack was the work of one person, who first fired at Ms Bhutto's vehicle and then set off a suicide bomb.

Video footage of the attack aired on TV had led to speculation that Ms Bhutto had been targeted by two people, working as a team.

The British police said its work had been complicated by failures to conduct an autopsy or preserve evidence from the crime scene.

However, the team said "the evidence that is available is sufficient for reliable conclusions to be drawn".

Their report appears to support the government's view, announced days after the attack on Ms Bhutto, that she died as a result of head injuries rather than gunshot wounds.

At the time, the PPP described the government's verdict as "dangerous nonsense".

What was the impact of Ms Bhutto's death?

Ms Bhutto was the dominant figure in Pakistani politics.

She had twice served as prime minister and was hoping that the PPP would emerge as a major player in the 2007 election, the first to be held since President Pervez Musharraf resigned as head of the army and became a civilian leader.

Western-educated and charismatic, she presented herself as a moderate, democratic force.

She was widely courted in the West, where it was hoped she could restore popular legitimacy to President Musharraf's faltering campaign against Islamist militants.

Her only son Bilawal, 19 years old at the time of her death, was installed as the PPP's president.

He has remained a figurehead, and the party has been led by Ms Bhutto's husband, Asif Ali Zardari, who has served as president.

Ms Bhutto and Mr Musharraf had been working on a power-sharing agreement.

The talks failed, leaving Ms Bhutto as a major rival to President Musharraf, rather than an ally.

Who could have targeted her?

The government blamed the attack on Baitullah Mehsud, a pro-Taliban tribal leader in South Waziristan region, abutting the Afghan border.

The CIA supported this view.

But a spokesman for Mr Mehsud denied any involvement, calling the accusation "government propaganda".

Nevertheless, pro-Taliban and al-Qaeda militants who have taken control of Pakistan's tribal areas along the Afghan border have been linked by many analysts to the attack.

They made no secret of their determination to kill Ms Bhutto after her return to the country in October 2007 following years of self-imposed exile.

However, elements within Ms Bhutto's party believed her killing could not have taken place without the collusion of senior figures in the military and political establishment.

They cited a letter Ms Bhutto released before her death in which she said she would hold President Musharraf's government responsible for any attempt on her life.

How did President Musharraf react?

Mr Musharraf appealed for calm immediately after the assassination, as disturbances broke out in various parts of the country. He also postponed the parliamentary election.

Mr Musharraf's popularity took a hammering during 2007, partly because of an intermittent military campaign against Islamist militants that alienated many and failed to achieve clear results.

Only weeks before Ms Bhutto's assassination, he ended a six-week period of emergency rule, during which he sidelined leading judges who were set to rule on whether he was entitled to stay on as president.

After the 2008 election, a coalition emerged led by the PPP.

Mr Musharraf stepped down as president and left Pakistan, living in exile in the UK and Dubai.

He returned in March 2013 in an abortive attempt to stand in national elections in May.

Prosecutors placed him under house arrest on allegations that his government failed to provide adequate security for Ms Bhutto.

Days later, the prosecutor in the Bhutto murder case was shot dead by gunmen as he drove to a court hearing.