Cullen’s Columbine includes a timeline entitled, “Timeline, Before,” which chronicles the series of events leading up to the Columbine mass shooting. In the hardcover edition, the timeline can be found on Pages 359-60, and is reproduced here in its entirety. 

SOPHOMORE YEAR

January 1997: The missions begin.

February 28, 1997: Wayne Harris starts his journal.

March 31, 1997: Dylan starts his journal.

Summer 1997: Eric and Dylan start at Blackjack; build first pipe bomb.

July 23, 1997: Dylan first mentions killing in his journal—possibly figuratively.

August 7, 1997: Eric’s website is reported to the police. It lists his “I HATE” rants.

JUNIOR YEAR

October 2, 1997: Eric, Dylan, and Zack are suspended for breaking into lockers.

November 3, 1997: Dylan first mentions a killing spree in his journal.

Unknown: Eric and Dylan steal from the school computer room.

January 30, 1998: Eric and Dylan are arrested for breaking into a van.

February 15, 1998: Deputies find a pipe bomb near Eric’s house.

February 16, 1998: Eric begins seeing a psychiatrist and soon starts taking Zoloft.

Spring 1998 [approximately]: Eric’s dad catches [Eric] with a pipe bomb.

March 18, 1998: Dylan warns Brooks Brown about Eric’s death threats.

March 19, 1998: Eric and Dylan conduct their intake interview for the Diversion program.

March 25, 1998: Eric and Dylan are formally sentenced in court.