President Barack Obama thanked the US intelligence community on Friday for helping track down and kill Osama bin Laden and warned remaining members of his al Qaeda network to watch their backs. “Make no mistake. This is not over …” Obama told members of the intelligence community gathered at Central Intelligence Agency headquarters in Langley, Virginia. “We walked off with his files — the largest treasure trove of intelligence ever seized from a terrorist leader.” Standing before a memorial wall covered in stars to honor members of the CIA killed in the line of duty, Obama said every member of al Qaeda should be “watching his back.”