Gunmen riding a motorcycle fired at the car of Federal Investigation Agency prosecutor Chaudhry Zulfizar Ali in the busy commercial area of Karachi Company at 7.30 am.
Ali, who was driving, was hit by several bullets and lost control of the car. The vehicle hit a woman crossing the road and she too died later in hospital.
His bodyguard, Frontier Corps trooper Farman Ali, was injured in the attack. Ali was heading for an anti-terrorism court in the garrison city of Rawalpindi for a hearing of the Bhutto assassination case when he was attacked, his son Nisar told the media.
The prosecutor and his bodyguard were taken to the state-run Pakistan Institute of Medical Sciences. Some doctors said Ali was killed instantly as several bullets had hit him in the face.
The gunmen escaped after the brazen shooting. No group claimed responsibility for the attack. Ali's son Nisar and unnamed colleagues were quoted by TV news channels as saying that the prosecutor had been receiving threats from a banned extremist group for some time.
His colleagues said he had continued pursing high-profile terrorism cases despite these threats. The prosecutor was gunned down at a time when there have been important developments in both the Mumbai attack case and Bhutto assassination case.
On April 13, a private witness from Karachi had identified Shahid Jamil Riaz, one of the accused in the Mumbai attack case, as the person who had bought inflatable boats used by the terrorists who assaulted India's financial hub in November 2008.
The Federal Investigation Agency had recently begun interrogating former president Pervez Musharraf over the 2007 assassination of Bhutto.