p>In 2020, mass shootings and hate crimes reached record highs. On January 6, 2021, a deadly mob stormed the US Capitol. In this eBook, we examine the factors that contribute to aggressive and brutal behavior, including its biological and genetic underpinnings, how intimacy and bias can lead to violence, how people become radicalized to commit acts of aggression, as well as certain psychological disorders and their role in violent behavior.