In Walter's third daydream, he is on the witness stand being grilled by the district attorney concerning his marksmanship with a pistol. Walter admits to owning the murder weapon,
"... my Webley-Vickers 50.80," he said calmly.
The people in the courtroom responded with "an excited buzz" as the "Judge rapped for order." Mitty himself "stilled" the commotion with a simple raising of his hand. He then admitted that, though his right arm was in a sling at the time,
"I could have killed Gregory Fitzhurst at three hundred feet with my left hand." Pandemonium broke loose in the courtroom.
It was this admission that caused the tumultuous reaction from everyone in the courtroom, including a woman who ended up "in Walter Mitty's arms." When the DA "struck at her savagely," Walter struck back in a typical Mitty-an manner, connecting with a punch to the attorney's chin.
ugh, the question got cuted off
Why does the courtroom become chaotic in Walter Mitty's 3rd day dream?