Maybe the RO was/is a DI. I've never been in the military, but suspect that DI's yell like they do for a few reasons.
If they yell, others hear also and the don't haver to repeat themselves 30 times a day.
Its easier to make a point to a lot of people at once even if only speaking to one individual by yelling.
People pay closer attention to someone who is yelling, vs someone who is not.
It makes it clear that he's doing his job and is serious.
?? Maybe. People don't seem to get mad at the DI for yelling, they realize he's just doing his job, and is sort of responsible for quite a few people at once.