So LHO was just aiming his rifle at the president. For what reason?
There is not a muzzle flash that is true. Maybe McCloy should have asked Brennan did you see him fire his rifle. He said he saw him "fire" his rifle in both the Dallas Morning News story and his FBI 11/22 affidavit. Your assuming he knew that discharged meant fire the gun instead of eject the shell.
"he saw this person take "deliberate aim" and fire a shot."
Brennan sees LHO aim the rifle, he hears the shot, and he sees him put the gun down to his side, stand there and view the damage but he did not see him he fire the shot? He never took his eyes off of the assassin.
So LHO was just aiming his rifle at the president. Lee Oswald was eating lunch in the first floor lunchroom at the time the President passed by the TSBD. He saw Junior Jarman and Harold Norman walk by the 1st floor lunchroom at 12:26 He was dressed in A REDDISH BROWN shirt and dark grey trousers.
The man that Howard Brennan saw with a rifle was much heavier than Lee Oswald and he was dressed in KHAKI colored clothes.