He was a bomb threat suspect so of course they would charge him with any petty crime he admitted to so they would get the excuse to further search his dorm, confiscate his laptop to get physical evidence of the bomb threat and detain him for further questioning. If he had said nothing and asked for a lawyer he'd still be in school.

This law professor explains why you should never talk to police, even if innocent http://youtu.be/6wXkI4t7nuc