Sharif was shot dead to end his ongoing investigation of corruption at the highest levels of Pakistan’s military. It's no secret that the Pakistani Generals, who run the Inter-Services Intelligence (ISI), work hand in hand with Afghan and Pakistani drug cartels. Sharif was working to expose their ulterior motive – to raise funds for global terrorists and fill their pockets – and was promptly silenced.
Sharif's murder silenced a very influential voice warning Pakistanis against US interests in their region and sent a chill down the spine of Pakistani journalists seeking to challenge global hegemony. The US is clearly behind Sharif's brutal murder — only the CIA has the resources, experience, and expertise to assassinate troublesome individuals in foreign countries. Despite this, there is very little chance that authorities will be able to conclusively trace the assassins and bring them to justice.