Did LHO fire a shot that missed everything? If so, when did he fire it?

[John Corbett]

   What are you basing, ".....almost 4 seconds between the first and second shots and almost 5 seconds between the second and third shots"?

Jiggle analysis shows blurred frames and a camera jump at Z155, Z227, and Z318. That's 72 frames between the first and second shots, and 91 frames between the second and third shots.
72 /18.3 = 3.934426229508197... seconds
91 /18.3 = 4.972677595628415... seconds

That's "almost" 10 seconds.

My calculator says it's almost 9.

That's a very long time and should have/would have attracted "eyeballs" from assorted Dealey Plaza positions toward the sniper's nest. According to Amos Euins, this did Not happen.     "POW..............POW/POW"!

It attracted Amos Euins. He saw two shots fired. Howard Brennan saw the last shot.

I really don't think Oswald was two concerned with whether anybody saw him or not. He just wanted to kill JFK. He succeeded. Why would you second guess him.