Patti Nielson was a part time teacher for art at Columbine High School. At the time of the massacre, she was on hallway patrol.

As the shooting unfolded, Patti Nielson talked on the phone with emergency services, telling her story and urging students to take cover beneath desks. According to transcripts, her call was received by a 911 operator at 11:25:05 a.m. The time between the call being answered and the shooters entering the library was four minutes and ten seconds. At 11:29:18, Eric Harris could be heard yelling "Get up!" on the 911 call. Several minutes later, Eric and Dylan left the library and Patti went to another room and locked herself in for 3 hours. At 12:08, Patti presumably heard Klebold and Harris shout "1!" "2!" "3!" in unison before hearing gunfire. She was discovered by the SWAT team at the school at 3:22 PM along with Lisa Kreutz, Brian Anderson, and 3 more library staff.