Review of European Studies; Vol. 14, No.1; 2022 ISSN 1918-7173 E-ISSN 1918-7181 Published by Canadian Center of Science and Education 54 Study 1: 630 Domestic-Terrorist, Mass-Murdering, Spree-Shooters Differ from 623 Controls and Study 2: 15 Domestic-Terrorist, Mass-Murdering, Spree-Shooters Differ From 23 Homicidal and 36 Controls on the Standard Predictor of Violence Potential and the MMPI-2/A: Implications Are to Use Computer Tests and Machine Learning Equations Robert John Zagar 1 , James Garbarino 2 , Brad Randmark 3 , Ishup Singh 4 , Joseph Kovach 5 , Emma Cenzon 5 , Michael Benko 5 , Steve Tippins 6 , Kenneth G. Busch 7 1 Consultant, Juvenile Division, Cook County Circuit Court, Chicago, IL, USA 2 Psychology Department, Loyola University Chicago, IL., USA 3 Cicero Illinois School District 99, Burnham School and Technology Department, USA 4 British College, Business Department, Nepal 5 Psychology Department, Calumet College of Saint Joseph, Whiting, IN., USA 6 College of Management and Technology, Walden University, Minneapolis, MN., USA 7 Private Practice, Chicago, IL., USA Correspondence: Robert John Zagar, 233 East Erie Street, Suite 404A, Chicago, Illinois 60611-4675, USA Received: December 1, 2021 Accepted: February 17, 2022 Online Published: February 28, 2022 doi:10.5539/res.v14n1p54 URL: https://doi.org/10.5539/res.v14n1p54 Abstract Study 1: 630 spree-shooters [1936-2021] (1,650 deaths; 3,123 injuries; 194 suicides [31%]), 623 controls logistic regression differences (F= 260.44, df=10/1242, R=.82, R 2 =.68, p<.01): (1) homicidal ideation; (2) planning-preparation; (3) stressful-life-event; (4) revenge-motive; (5) acquired-multiple-weapons; (6) elicited-concern; (7) school-location; (8) personal-grievance; (9) suicide; (10) current-student. Study 2: 15 spree-shooters differences, adult, teen: [SP] violence (F=17.48, 123.09); [MMPI-2/A] infrequency (F=92.15, 17.22); lie (F=13.13, 33.91); depression (F=37.76, 26.18); psychopathic-deviance (F=44.66, 57.45); paranoia (F=50.58, 23.92); schizophrenia (F=53.85, 21.69); alcohol (F=42.01, 16.84); addiction (F=57.34, 38.88) compared with 23 homicidal, 36 controls. Spree-shooter loss (1936-2021) = [$2,416,042,490 (630 @ $3,834,988.08) + $6,327,730,332 (1,650 @ $3,834,988.08) + $105,474,702.96 (3,123 @ $33,773.52) = $8,849,247,525.36] + [insurance, tax-increases $11,504,021,782.97 ($8,849,247,525.36 x 1.3] =$20,353,269,308.33. Projecting 2021 to 2105 insurance industry with no computer tests, machine learning equations, $40,706,538,616.66, 3,330 deaths, 6,246 injuries, 388 suicides. Projecting 2017 U.S. Church pedophilia loss (2012-2037, 2038-2056, 2057-2082, 2083-2107), $5,719,865,400 x 5 = $28,599,327,000, 5,679 x 5 = 28,395 victims. Keywords: spree shooters, computer tests, machine learning equations, logistic regression differences, controls, homicidal, costs to insurance industry and U.S. Roman Catholic Church Introduction After verbally and physically threatening a teacher, 17-year-old Robert L. is jailed in a juvenile detention center for a month. Exhibiting good behavior and no confrontations, he is slated to be released from jail soon. The counselor has a nagging doubt, thinking, “There is something going on. But I don’t know what?” Following a computer personality test and machine learning equation for violence potential, what should the judge and the counselor do? Is Robert L. a spree-shooter or is he just another aggressive, impulsive adolescent? Daily, this is a question posed by thousands of offenders globally. This article will address the issue of spree-shooters and how to find them before the shooting occurs when high risk persons come to courts, hospitals, human resources and schools, by using computer tests and machine learning equations. Specifically, the reader will learn that regardless of when and where the violence-prone high risk person appears, computer tests and machine learning equations can intercept and divert the individual from costly domestic-terror, mass-murder, spree-shooting Domestic-terrorists, mass-murderers, and spree-shooters plague every country. Little, vigorous, scientific evidence