Extra police were assigned inside buildings at Columbine High School Friday and students are not allowed to leave the campus because of threats penciled on the walls of two bathrooms and a sidewalk.
Jefferson County Sheriff's spokeswoman Jacki Tallman says the school lockdown is very low-key and is not disrupting classes. She says the threats did not specify an individual or group and were very vague and very short.
On April 20th, 1999, teen gunmen Eric Harris and Dylan Klebold fatally shot 12 students, one teacher and themselves at the school. The school has received a number of threats in the years since the killings and several times has gone to a form of lockdown in response.