Imam - real name Sultan Amir Tarar - was kidnapped last April along with another former ISI officer, Khalid Khwaja and British journalist Asad Qureshi and his driver. Khwaja was later murdered, but Qureshi was released after his family paid a large ransom.
It is believed the men were kidnapped by a group calling itself the Punjabi Taliban, made up from expelled members of the Pakistan Taliban and the sectarian Lashkar-Jhangvi group. Some of the group's leaders, including Usman Punjabi, died last August in a shoot-out over how Qureshi's ransom should be divided.
Col. Imam and Khwaja were both Taliban sympathisers and had accompanied Qureshi to Waziristan so that he could make a film. However, the kidnappers believed the two former ISI officers were spies. Despite attempts to secure their freedom by Taliban officials the two men were killed.
Videos were made of both men before they were killed. Khwaja was shown allegedly confessing to being a CIA spy, while Col Imam begged the authorities to do something to save him.
Once report says that he was killed when his family failed to deliver a $590,000 ransom. The killers now say they want a ransom before they will hand over the body.