Is it possible that Nicolas Maduro will be the first arrest? If he were a normal president, then he'd be a civilian. But, he's running the country as a dictatorship and has been controlling the army, making him if not de jure, then de facto military leader, by extension, non-civilian.
There hasn't been much news about him, since Barr had that video stream, talking to everyone about the unsealed charges being brought against him and some high-level people working with him. We haven't heard anything from them in ages. Quiet often means busy. So, my guess is they've been tracking him (and his people) down, the whole time the rest of the world has been distracted by the CoronaVirus.
The other thing is, to have a "head of state" (legitimate or not) go down is huge. This would be a message to everyone else, saying: no one is beyond reproach. It would pave the way for everyone else to be brought to justice.
The other thing is, there's some sketchy history around Maduro. He's another high-level person with suspect heritage (a lot of the same concerns as surrounding Obama). So, it would set up a nice precedent for Obama in another regard.