This is something the media is reporting, so assume they're lying about at least one thing and leaving out at least one key detail. Remember the "Maryland man" that got deported for no reason at all except oop, turns out he was MS-13 affiliated?
The major problem with this story is that if you have a green card, you are here on a residency visa. Your visa is still valid if you lose your physical card, which you can just get replaced. You can't be deported unless you've done something that violates the terms of that visa. If they nabbed him and deported him, it's because some kind of red flag came up in the system. So what was it?
Since we know he was a refugee from Pinochet, he was most likely a Communist. Was he involved in subversive political activities here in the States? Did he traffic drugs? Did he just fail to renew his visa for 20 years? Additionally, if he got deported to Guatemala, it's because Chile wouldn't take him.
Conclusion: We're not being given the full story.