Okay so who shot bob?
We need to reduce the suspect first
1. From the shadow we knew he's male since all the girls have distinct boob and not tall enough
2. It has to be an already introduced character
For such important character, author always introduce it first
So that left us with a few suspects.
Yuichi, glasses, prep, masochist, baldy, JSDF, and Cultist.
Let's eliminate them even more
Glasses and prep will not shot their team mate
Beside they won't disobey Yuichi or move without his permision
Baldy and Masochis clothes is different from shooter
Baldy wear sleeveless and Masochist wear black shirt
So that mean the suspect left is JSDF, Cultist, and Yuichi.
Fourth suspect is possible as long he already introduced.
Someone like kuroki or bob's former team mate