[penagwin]

> Kim was taken into custody on Monday—identified as one of the few Harvard wireless users who was also on Tor at the time. When interviewed by an FBI agent and an officer with the Harvard University Police Department that night, Kim admitted to sending the bomb threat emails and said that he acted alone.

Based on this it sounds like if he hadn't confessed he wouldn't have been caught. After all, it would still be on the prosecutors to prove he used tor to send the threat, instead of just using it out of paranoia or something.