He stole computer code from his employer. This is a rather straight forward criminal case. It involves the FBI because GS and its computer code conduct business in multiple states, across state lines.
Once the crime is proven and he’s convicted GS can go after him for damages.
Lots of Russian coders are like this. Unscrupulous.
“He stole computer code from his employer.”
Well, technically he just copied it. Stealing implies that the employer no longer has it, which isn’t true, and that is part of his defense. They charged him under laws that have to do with “tangible” theft, while code is not tangible.