http://wid.ap.org/documents/okc/okcdoc2.pdf
"A witness to the explosion named Grossman claimed to have seen a pale yellow Mercury car with a Ryder truck behind it pulling up to the Federal Building. Mr. Grossman further claimed to have seen a woman on the corner waving to the truck. ATSAIC McNally noted that this fact is significant due to the fact that the security video shows the Ryder truck pulling up to the Federal Building and then pausing (7-10 seconds) before resuming into a slot in front of the building. It is speculated that the woman was signaling the truck when a slot became vacant."
First, this is interesting because the person noting the significance is the Assistant to the Special Agent in Charge(ATSAIC). If there was a tape, he should know.
But even better (for me, anyways :) ), is that the tape is referred to as "the security video". not "A" security video, not "some" video, but "the security video". It seems obvious that the writer expects the readers to be familiar with the existence of the video.
"Security video tapes from the area show the truck detonation 3 minutes and 6 seconds after the suspects exited the truck"
"Security video tapes"?
The tape probably shows clear evidence of explosives inside the building.