PITTSBURGH - Campus police, federal authorities, and experts are stumped by more than 20 bomb threats since mid-February that have prompted building evacuations on the University of Pittsburgh campus, caused some professors to move classes or offer them online, and led some students to stay off-campus.
Although the threats received more attention after a gunman fatally shot one person and wounded several others before he was shot dead by campus police at a University of Pittsburgh Medical Center psychiatric hospital on March 8, the string of threats actually began on Feb. 13.



