According to the shooter's respective journals and video tapes, it is believed by investigators that the pair intended to detonate their propane bombs in the cafeteria at the busiest lunch hour,<ref>See,{{Citation|title=Murder forAt example,Columbine KateHigh Battan,School who(Mass wasShooting leadDocumentary) detective| onReal the case: "Eric Harris had even gone so far as to study how many people were in the cafeteria at any given time during the lunch hour. … Approximately 450 [at peak period] is what he was estimating, and we had 455 kids down there." See [Crime|url=https://www.youtube.com/watch?v==D9mUpUHk3nE&t|language=27m40s "Murder At Columbine High School"].en|access-date=2023-02-12}}</ref> killing hundreds of students. After this, they would shoot and stab survivors, as well as lob bombs. Bombs set in their cars in the parking lot would also eventually detonate, killing more students as well as possibly any police officers, paramedics, firemen, or reporters who had come to the school.<ref name=ten /><ref>{{cite news|url=http://news.bbc.co.uk/2/hi/americas/329303.stm|title=Columbine killers planned to kill 500|date=April 27, 1999|access-date=October 15, 2014|archive-url=https://web.archive.org/web/20100515095812/http://news.bbc.co.uk/2/hi/americas/329303.stm|archive-date=May 15, 2010|url-status=live|work=BBC News}}</ref>{{efn|Investigators speculated they were supposed to detonate after the massacre and injure first responders.<ref>''The Columbine School Shootings'' {{ISBN|978-1-420-50138-4}} p. 65</ref>}} However, this failed to occur since the bombs in the cafeteria and cars failed to detonate.<ref>{{cite news|url=https://www.theguardian.com/world/2009/apr/25/dave-cullen-columbine|title=The Reluctant Kller|access-date=July 15, 2020|newspaper=[[The Guardian]]|date=April 25, 2009}}</ref>
Several official sources claim they planned to shoot the fleeing survivors from the parking lot, but moved to the staircase on the hill at the west side of the school when the bombs failed.<ref>e. g. {{cite web|url=https://schoolshooters.info/sites/default/files/Columbine%20-%20Governor's%20Commission%20Report.pdf|title=Governor's Report|page=26}}</ref> Other sources claim the top of the staircase where the massacre began was their preferred spot to wait for the bombs to go off all along.<ref>{{Harvnb|Krabbé|2012|pp=31, 41}}</ref>{{efn|Klebold made notes prior to the massacre which included "Go to the outside hill, wait. When first bombs go off, attack."<ref name=suspdk/>}}
