Introduction: Scope of the problem, definitions and concepts / Jacob Holzer, Andrea J. Dew, Patricia R. Recupero, and Paul Gill -- Historical aspects and evolution of lone-actor violence / Mark Hamm and Tammy Ayres -- Case reviews in lone-actor terrorism incidents / Jacob Holzer, Olivia Zurek, and Lauren Simpson -- Clinical psychiatric and neuropsychiatric aspects of lone-actor terrorism / Robert P. Granacher, Jr., Danielle B. Kushner, and Jacob Holzer -- Psychoactive agents and mental disorders in lone-actor terrorism / Michael Arieli, Aviv Weinstein, Uri Ben Yaakov, Ronnie Berkovitz, Alina Poperno, Hagit Bonny-Noach, and Robert P. Granacher, Jr. -- Developmental aspects of lone-actor terrorists / Karl Mobbs, Gen Ignatius Tanaka, and Terry R. Bard -- The role of psychometrics in investigating lone-actor terrorism / Nancy P. Moczynski, Allen Schiller, Theodora Farah, and Eric Drogan -- Understanding lone-actor violence through linguistic analysis / Isabelle W.J. van der Vegt, Bennett Kleinberg, and Paul Gill -- Propaganda and lone-actor terrorism / Eric Drogan -- Lone-actor mass casualty events and linkages to organized violent Salafist-Jihadist inspired terror groups / Andrea J. Dew and Daniel Starr -- The internet and social media as an enabling force / Patricia R. Recupero and Samara E. Rainey -- Geographic context : domestic vs. international lone-actors / Christopher Jasparro and Suzanne Levi-Sanchez -- Means, mechanisms, and trends of operationalizing violence / Christopher Winter, Ramón Spaaij, and Marilyn Price -- Role of forensic mental health and lone-actor violence / Ashley H. VanDercar, Ryan C. Wagoner, Phillip J. Resnick, Frank Farnham, and Emily Corner -- An ethics analysis of lone-actor terror and society's response / Danielle B. Kushner and Philip J. Candilis -- Law enforcement response to lone-actor incidents at the local through federal levels / Douglas Brennan, Mark Concordia, and Michael Madden -- Post-9/11 U.S. Military and intelligence approaches to lone-actors / Corri Zoli -- U.S. Legal perspectives : legislative, intelligence, and law-enforcement aspects / Jeffrey H. Smith, Amy Jeffress, Christopher E. Beeler, and Tian Tian Xin -- Pursuing lone-actor terrorists : U.K. counterterrorism law and policy / Stuart Macdonald -- Lone-actor terrorism : understanding online indoctrination / Steven Hassan, Jon Caven-Atack, Mansi J. Shah, and Simran Malhotra -- Hatred and grievance as constructs in lone-actor terrorism / Jacob Holzer, Arya Shah, Eric Drogan, and Robert P. Granacher, Jr -- Comparing lone-actor terrorism to other high-threat groups / Jacob Holzer, Emily Threlkeld, William Costanza, Patricia R. Recupero, and Samara E. Rainey -- A risk analysis framework of lone-actor terrorism / Noémie Bouhana, Emily Corner, and Paul Gill -- A framework for preempting lone-actor terrorists during the pre-incident phases / Joshua Sinai -- Threat assessment : the TRAP-18 and application to a lone-actor terrorism incident / J. Reid Meloy and Jacob Holzer -- Use of threat and risk assessment tools in the evaluation of lone-actor terrorists / Hy Bloom, Reem Zaia, and Arya Shah -- Developing a risk assessment and intervention strategy : future directions in research and practice / Jacob Holzer, Andrea J. Dew, Patricia R. Recupero, and Paul Gill.