About two hours after the initial shootings, Cho entered Norris Hall, which housed the Engineering Science and Mechanics program among others. In a backpack, he carried several chains, locks, a hammer, a knife, two handguns with nineteen 10- and 15-round magazines, and nearly 400 rounds of ammunition. With the locks and chains, he chained the three main entrance doors shut and placed a note on one, saying that attempting to open the door would cause a bomb to explode. Shortly before the shooting began, a faculty member found the note and took it to the third floor to notify the school's administration. At about the same time, Cho had begun to shoot students and faculty on the second floor. The bomb threat was never called in. The first call to 9-1-1 was received at 9:42 a.m.