Investigators for 9/11 families examine video taken by man with ties to Saudi intelligence referencing a "plan"

For more than two decades, the U.S. position has been that al Qaeda acted alone on September 11th, but a newly public video has raised questions about whether the Saudi government provided crucial assistance to the hijackers during the 9/11 terror attacks.

Omar al-Bayoumi, whom the FBI says was an operative of the Saudi intelligence service with close ties to two of the 9/11 hijackers, can be heard on the video, which was unsealed in federal court this week and obtained by 60 Minutes. The 1999 video was taken within 90 days of the time when senior al Qaeda planners were deciding on 9/11 targets, Richard Lambert, a retired FBI agent who led the initial 9/11 investigation in San Diego, said.

"It is another very large brick in a massive wall of evidence that at this point indicates the Saudi government was complicit in the 9/11 attacks," Lambert said.