Early this morning, at a showing of the new Batman movie, a gunman burst through an emergency exit door and into a theater in Aurora, Colorado. James Eagan Holmes, 24, shot at the ceiling, threw two gas canisters (likely tear gas) and then began firing on the audience. He killed 12 people and wounded 59 others, many of whom were rushed to area hospitals.

Holmes, 6-feet tall and wearing a riot helmet, goggles and a bullet-proof vest, was arrested outside the theater. He carried an assault rifle, a shotgun and a hand gun, as well as tactical body armor and a gas mask. Police found ammunition in his car and are currently working to diffuse numerous booby-traps in his house.

President Obama was scheduled to hold a campaign rally today in Florida, but in lieu of political remarks, he spoke about the Colorado shooting.

“If there is any take away from this, it’s that life is fragile,” he said. “Our time here is limited, and it is precious.”

Whenever tragedies like this occur, one lesson is certainly that human life is delicate, full of unpredictable and sometimes horrific events. As investigations continue, however, the public discussion will inevitably turn to how an attack like this could be prevented in the future. No matter what experts suggest and elected officials demand, the hard reality is that events like these cannot always be prevented. A motivated individual with the means to acquire weapons and desire to take human life can always find opportunity to execute their deadly plans, as evidenced in school shootings, terrorist attacks and other tragedies.

Perhaps movie theaters will begin using metal detectors, though that would likely not have stopped Holmes’ attack (as he entered through an emergency exit). There may be calls for stricter gun controls and limits on the kinds of equipment the public can purchase (such as riot helmets). But this too cannot stop a person’s plans to kill en mass. Indeed, there are steps that could make it more difficult to launch such an attack, but it is an inevitable reality in modern America that a “lone wolf” attacker is often impossible to detect before it is too late.

Even as the Department of Homeland Security and other law enforcement and emergency management organizations work to anticipate and mitigate threats, there are some things they simply cannot foresee or prevent. This isn’t the first time a lone gunman has succeeded in attacking a crowd, and it will not be the last. Yet, despite the impossible task of halting these kinds of threats, Americans should maintain their resolve to observe their surroundings for the specter of evil intent. As DHS encourages, when you see something, say something.

The national effort in this regard, plus the ongoing efforts of security departments, can make a difference and hopefully stop some impending tragedies. The President was right in his sentiment that Holmes’ attack highlights the fragility of human life, but there is perhaps another lesson. The threat of attack is never-ending, be it from terrorist organizations or individual actors. Americans must maintain their commitment to collectively guard against these threats. The Colorado shooting likely could not have been prevented, but Holmes’ actions underscore the constant need for citizen vigilance. Offer prayers for the dead and wounded, but keep your guard up. Sometimes, that is the best we can do.

Justin Hienz is Editor for Security Debrief. He blogs primarily on radicalization, aviation security, religious and Middle Eastern affairs, and communications. Read More