(CNN) -- A suicide bomber has attacked and killed Bilal Shaikh, the security chief of Pakistan President Asif Ali Zardari, Police Superintendent Raja Umer Khitab said.
The attack happened as Shaikh's car pulled up to buy fruit from a roadside stall in Karachi, Khitab said.
Khitab told CNN that his early assessment is that the bomber was on foot and approached the passenger window where Shaikh was sitting and set off the bomb. Shaikh's vehicle was bullet proof, so Khitab believes the shock wave of the blast killed the security chief.
The attacker also killed Shaikh's driver and a fruit stall vendor who was on the side of the road.
Video showed wreckage of a white SUV.
Shaikh traveled with two police vehicles, one in front and one behind, Khitab said, and at least 7 police officers have also been injured in the bombing.
"It's not known if Mr. Shaikh had received any threats, but he was definitely the target of this attack," Khitab told CNN.
The port city of Karachi is Pakistan's largest.
CNN's Saima Mohsin in Islamabad contributed to this report.