The pics from the Zapruder film did not become public until several months after the shooting, when Life published their article and the frame-by-frame pics. Reportedly, quite a battle ensued for the rights from Abraham Zapruder, after he initially agreed early on to sell it to Life--then got some bigger offers.
The actual movie wasn't shown for 15 years or so, as I recall.
As an aside, when I visited Dealey Plaza in 2005 (after being a Kennedy assassination buff 40 years), I was completely surprised at how relatively close the distance was from the 6th story School Book Depository window to the "X-marks-the-spot" head-shot location. And also how close Zapruder actually was to the fatal bullet strike (about 30-35 feet tops).
The Plaza was so much smaller than I had imagined after all those years of reading and watching films about it.
I visited the 6th Floor museum in 96, before the window was roped off, and had a chance to look out down the line of fire. I also was impressed by how easy a shot it must've been with a scoped rifle. It felt like you were right on top of the stretch of road the president was hit on.