Austin Miller's Warren Commission Testimony (back to the list of witnesses)
http://mcadams.posc.mu.edu/russ/m_j_russ/comp.htm#list

(Miller was standing on the triple overpass)

Mr. BELIN - Well, describe what happened. Did you see the motorcade come by?
Mr. MILLER - Yes sir; it came down main street and turned north on Houston Street and went over two blocks and turned left on Elm Street. Got about halfway down the hill going toward the underpass and that is when as I recall the first shot was fired.
Mr. BELIN - Did you know it was a shot when you heard it?
Mr. MILLER - I didn't know it. I thought at first the motorcycle backfiring or somebody throwed some firecrackers out.
Mr. BELIN - Then what did you hear or see?
Mr. MILLER - After the first one, just a few seconds later, there was two more shots fired, or sounded like a sound at the time. I don't know for sure. And it was after that I saw some man in the car fall forward, and a women next to him grab him and hollered, and just what, I don't know exactly what she said.
Mr. BELIN - Then what did you see?
Mr. MILLER - About that time I turned to look toward the - there is a little plaza sitting on the hill. I looked over there to see if anything was there, who through the firecracker or whatever it was, or see if anything was up there, and there wasn't nobody standing there, so I stepped back and looked at the tracks to see if anybody run across the railroad tracks, and there was nobody running across the railroad tracks. So I turned right straight back just in time to see the convertible take off fast.
Mr. BELIN - You mean the convertible in which the President was riding?
Mr. MILLER - I wouldn't want to say it was the President. It was a convertible, but I saw a man fall over. I don't know whose convertible it was.
Mr. BELIN - Where did the shots sound like they came from?
Mr. MILLER - Well, the way it sounded like, it came from the, I would say from right there in the car. Would be to my left, the way I was looking at him toward that incline.
Mr. BELIN - Is there anything else that you can think of that you saw?
Mr. MILLER - About the time I looked over to the side there, there was a police officer. No; a motorcycle running his motor under against the curb, and jumped off and come up to the hill toward the top and right behind him was some more officers and plainclothesmen, too.
Mr. BELIN - Did you see anyone that might be, that gave any suspicious movements of any kind over there?
Mr. MILLER - No, sir; I didn't
Mr. BELIN - Did you see anyone when you looked around on the railroad tracks, that you hadn't seen before
Mr. MILLER - No, sir; I didn't.