A Catholic university in Chicago has been closed "indefinitely" because of threats scrawled on the walls of a residence hall, officials said. The threats came less than two months after a former student killed five people at nearby Northern Illinois University and days before the first anniversary of the Virginia Tech massacre, the worst school shooting in US history. "On the considered advice of the multiple law enforcement agencies pursuing the case, we have chosen to close Saint Xavier University indefinitely beginning tonight due to the specific nature of the second message found on April 10, which read: "Be prepared to die on 4/14," university president Judith Dwyer said in a statement posted on the school's website.