Terrorist attacks and mass shootings have changed the threat landscape. In the old-world paradigm, planes were the target and metallic objects were the key concern. In the new-world paradigm, anything can be a target. Thus, the security response needs to shift from reactive to proactive. Artificial intelligence (AI) is the key to moving from a reactive to proactive security response. Three specific applications of AI in the physical security field enable organizations to prevent attacks, not just react to them.