Exactly how does one “study to be a US Marshal”?
You study for the exam:
https://www.usmarshals.gov/careers/deputy_exams.html
Here is a study guide:
https://www.usmarshals.gov/careers/prep_guide.pdf
Shoot, those guys need to know the law better than most lawyers. Lots and lots of studying involved. I’m guessing, because I really don’t know, that he was either in the academy or getting ready to go.