Militants attacked the vehicle of Senior Superintendent of Police (SSP) Muhammad Illyas who was on his way to market, killing the officer, his wife, son and five-year-old granddaughter.
The targeted killing took place when the Illyas was going to the market with his family and his vehicle was attacked by four gunmen on motorcycles in the Nawa Kili area of Quetta, officials said.
The targeted killing of Illyas is the second deadly terrorist attack on a senior police official in Quetta in a week's time.
A suspected suicide bomber killed Additional Inspector General Telecommunications Hamid Shakeel and three other police officers in a targeted attack in Quetta on November 9.
More From This Section
According to another police official, SSP Illyas was going with his entire family to the market when the attack took place with the gunmen on motorcycles surrounding his vehicle and opening fire from two sides.
Balochistan has been rocked by a series of attacks which raised concerns about a growing militant presence, including those affiliated with Islamic State, which has claimed several bombings in the restive province.
The unrest has raised security concerns for projects in the USD 50 billion China Pakistan Economic Corridor, a transport and energy link from western China to Pakistan's southern Gwadar port.
At least six police commandos and a civilian were killed last month when an explosives-laden vehicle rammed into a security force's convoy on the Quetta-Sibi Highway.
In June this year, 14 people, including seven policemen, were killed and 21 others were injured in a suicide car bombing on Gulistan Road in Balochistan.