Us Schools Lockout

Colorado's Columbine High School and at least 20 surrounding schools were placed under a "lockout" security alert on Tuesday as authorities cited a "potential credible threat" posed by an 18-year-old woman described as armed and "extremely dangerous."

Colorado's Columbine High School and at least 20 surrounding schools were placed under a "lockout" security alert on Tuesday as authorities cited a "potential credible threat" posed by an 18-year-old woman described as armed and "extremely dangerous."