They need to lock up the crazy moron soon. Was he a teenager or a college student?
This stuff happened long before the Patriot Act.
I believe a freeper got a visit from the Secret Service for saying something similar about Clinton. Then right after election 2000, someone from DU also had some explaining to do, for a (half)joking scenario he'd laid out whereby Gore could still become president if he were to run for Congress that fall, be immediately elected Speaker of the House, and then succeed to the Presidency after Bush and Cheney had both been assassinated at the same time.
This is what the Secret Service does now, after a spate of successful and attempted assassinations starting with Kennedy. If you don't want to spend time with them, be careful how you express your desire for the president's death. That is all...
Anyway, the Secret Service are not haunting fan lists looking for threats. Probably someone in your group, who also found that sentiment reprehensible, dropped a dime on the guy.