At even the best-prepared universities, there is no playbook for handling the crush of tough decisions that comes after a mass shooting rocks an otherwise quiet campus. While colleges and universities have always had tragedies, recent occurences like the shootings at Northern Illinois University and Virginia Tech have fundamentally changed the way they view things. They must think about security at all times. This article includes advice on preventing and preparing for emergencies. Suggestions include: (1) Encouraging students, administrators, staff members, and law-enforcement officers to communicate regularly about students who are struggling or have threatened violence; (2) Preparing students to respond during these emergencies; (3) Developing threat-assessment teams that are capable of gathering disparate pieces of information and assembling them; and (4) Carefully considering what types of alert systems--text messaging, e-mail, voice mail, sirens--make the most sense for the college or university.