An indispensable resource for anyone interested in learning about the long-term impact of the 1999 Columbine High School shooting, Columbine, 20 Years Later and Beyond provides a comprehensive look at how the event unfolded, what has changed since the attack, and how this information can be used to prevent future mass shootings.Authors Jaclyn Schildkraut and Glenn Muschert, both experts on mass shootings, share their broad understanding of this tragedy and its aftermath. Columbine became the measuring stick against which all other mass shootings would be compared, and this book details with great sensitivity the ensuing changes to school security, law enforcement's response to active shooter situations, threat assessment practices, legislative efforts, and media coverage of unfolding situations. With delicacy and tact, Schildkraut and Muschert help to answer the painful question raised by a stone on the wall of the Columbine Memorial: What have we learned?.