Near the end of Haskell Wexler
's 1969 film "Medium Cool
" are several scenes shot in 1968
in the streets of Chicago
, during the Democratic Convention. It's actual footage of Chicago police
trying to stop a procession of peaceful demonstrators making their way to the Convention center. In one scene there's a line of cops with riot shields, facing the oncoming demonstrators.
The camera is near the cops, looking at them, when suddenly a tear-gas canister is thrown and lands a couple of feet in front of the camera so that the gas blows towards it. Someone, presumably the cameraman, coughs. A second later somebody close by exclaims (probably to the cameraman), "Look out Haskell, it's real!"