Having one door that goes in and out of the school, having armed police officers at that one door," Cruz said the day of the shooting. “Have one door into and out of the school and have that one door, armed police officers at that door.” The remarks by some of the most influential Republicans underscore how the focus on doorways has become one of the most common GOP responses to school shootings in a nationwide debate around school security that largely began after the shooting at Columbine High School in Littleton, Colorado, in 1999.