This 911 call was placed by teacher Patti Nielson during the April 20, 1999, shooting at Columbine High School in Colorado. During the call, shooters Eric Harris and Dylan Klebold enter the library where Nielson, three teachers and 52 students were taking cover. Only the first five minutes of the call were released to the public. Harris and Klebold are heard yelling on the tape. After the tape cuts out, they open fire, killing ten and injuring many others. Nielson survived the shooting by locking herself in a break room with an injured student and three library staff members.