She pointed to the 1999 Columbine High School massacre, where 10 of the 12 people that were killed "perished inside the school library — a room where they believed they could hide safely."

Source: https://theweek.com/mass-shootings/1021036/the-controversial-run-hide-fight-response-in-active-shootings

To do that, reporters attempted to identify every act of gunfire at a primary or secondary school during school hourssince the Columbine High massacre on April 20, 1999.

Source: https://japantoday.com/category/world/number-of-us-children-killed-by-guns-hit-record-high-in-2021-study