I have often said our biggest vulnerabilities can be found in places where people congregate. Human targets are often selected by bad guys simply because they are part of a crowd. This goes against our natural instinct to believe bad actors won't pursue us in a crowd and will wait until we're alone. This is true for some attackers. However, terrorists and active shooters pick crowds because our intolerance towards suffering any casualties makes a target-rich environment like a mall an almost irresistible target. The meme above personifies how often we protect against the last known vulnerability and losing sight of the vulnerabilities we create or ignore.
Here's the scene of a major airport's TSA screening area. Notice the crowd aka potential targets.
