Who killed Rafik Hariri?

The latest theory focuses on the role of Ali Salah Haj. According to the story, Haj was a security escort close to Hariri until Hariri suspected him of informing on him to the Syrians. Haj was then reassigned to an intelligence post in the Bekaa valley, but seems to have played a controversial role in the initial investigation of Hariri's death by removing Hariri's car from the scene of the explosion that killed him.