Two of the worst targeted attacks on American police officers in recent history occurred within eleven days of each other. Although it seems clear their proximity was not merely attributable to chance, the connection between these incidents, and the implications for understanding copycat violence, have never been fully explored. This study analyzes the perpetrators of these attacks from a “thresholds of violence” perspective, which suggests the first actor in a sequence is more likely to be disturbed and violence prone, while subsequent actors are typically less disturbed but more socially influenced. Results suggest the thresholds model has both merits and limits. The first attacker did have more psychological problems and violence in his past, and the second did seem more influenced by violent role models. However, there were also many similarities between them, and both attacked due to a combination of internal and external factors. If this study's findings are generalizable, higher risks of becoming a copycat offender may exist for individuals who have (1) personal similarities with previous attackers, (2) a history of psychological problems, (3) a history of interest in violent actors, and (4) recent escalation in their online behavior. Recommendations are offered for future research, offender profiling, and violence prevention.

最近历史上针对美国警察的最严重的两次针对性袭击发生在 11 天内。尽管很明显它们的接近不仅仅归因于偶然，但这些事件之间的联系以及对理解模仿暴力的影响从未得到充分探索。本研究从“暴力阈值”的角度分析了这些攻击的肇事者，这表明序列中的第一个参与者更有可能受到干扰和暴力倾向，而随后的参与者通常较少受到干扰但受到更多社会影响。结果表明阈值模型既有优点也有局限性。第一个攻击者过去确实有更多的心理问题和暴力行为，而第二个攻击者似乎更受暴力榜样的影响。然而，他们之间也有很多相似之处，都是内因和外因共同发起的攻击。如果这项研究的发现具有普遍性，那么对于具有以下特征的人来说，成为模仿犯罪者的风险可能会更高：(1) 与以前的攻击者有相似之处，(2) 有心理问题的历史，(3) 对暴力演员感兴趣，以及(4) 近期上网行为升级。为未来的研究、罪犯分析和暴力预防提供了建议。(3) 对暴力行为者感兴趣的历史，以及 (4) 最近他们的在线行为升级。为未来的研究、罪犯分析和暴力预防提供了建议。(3) 对暴力行为者感兴趣的历史，以及 (4) 最近他们的在线行为升级。为未来的研究、罪犯分析和暴力预防提供了建议。