Students are key to making sure a campus is safe and secure. That was obvious during a recent drill at the University of Missouri, which locked down the campus.

The problem? Students equipped with their ID cards could still enter or exit their dorms, according to this report from a Missouri television station. While the red alert closed the doors on any outside threats, at least four students walked right through the front door.

"We tell our students all of the time that they need to be cautious...anytime the hall is locked they need to not be letting people come in behind them. That's hard for students to do sometimes," said a university spokesperson.

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