It was a "you can resign with severance (and sign this release), or I can fire your ass and you get diddly" situation. He took the paperwork home with him, and he has 21 days by law to decide.
Technically, I didn't do it to him - my boss did. But, I'm HR, so anything like this has my stamp all over it, and I was the only other person in the meeting where he was told.
I came across the lady who lives in the adjoining cubicle today. She was crying softly. She asked me if I got his key and if I was sure he wasn't ever coming back. That tells me it was the right call.