(Just imagine. They have a tape of this)
A lot of people watching the motorcade were filming it. The FBI was going around tracking bystanders down and confiscating their film cameras. Many never got them back nor the film. NBC might have film that they didn’t want to release the the public to destroy the Warren Commission narrative of a single shooter.
I have no doubt that a lot of people were also filming the assassination attempt at Butler. But the FBI swooped in and confiscated video that proves the Secret Service involvement.