With some police shootings of minorities, it's the opposite. An invisible "gun" is "seen" in the hand of the compliant "suspect" by a racist officer, then after "appropriate measures" (learned in so-called "training"), the now-dead suspect's "gun" is no longer seen.
I'm not seeing the relevance to the Tippit situation. Oswald was white. The only policeman at the scene was killed by him. The shooter obviously had a gun. In the course of human history, there have been such situations as you describe, but so what in this context? Point being that if a witness hears a gunshot and immediately looks in the direction of the shooting to see one man with a gun next to the victim it's accurate to say that they witnessed the shooting. There was no one else at the Tippit shooting with a gun. No one other than the person with the gun could have committed the act. Multiple witnesses identified Oswald as the "shooter" via his possession of the gun at the scene of the shooting. Marham saw him commit the act. Only a pedantic CT contrarian would split hairs about characterizing these witnesses as seeing Oswald literally pull the trigger. No one saw John Wilkes Booth pull the trigger to kill Lincoln. They heard the gun shot, looked in that direction, and saw Booth with the gun. No one in their right mind would ever suggest there is doubt that these witnesses had seen the shooter.
