On January 30, 1998, Harris and Klebold broke into a locked van to steal computers and other electronic equipment. An officer pulled over the duo driving away. Harris shortly after admitted to the theft. They were later charged with mischief, breaking and entering, trespassing, and theft. They both left good impressions on juvenile officers, who offered to expunge their criminal records if they agreed to attend a diversionary program which included community service and psychiatric treatment. Harris was required to attend anger management classes where, again, he made a favorable impression. The boys' probation officer discharged them from the program a few months ahead of schedule for good behavior. Of Harris, it was remarked that he was "a very bright individual who is likely to succeed in life", while Klebold was said to be intelligent, but "needs to understand that hard work is part of fulfilling a dream." A couple of months later on April 30, Harris handed over the first version of a letter of apology he wrote to the owner of the van, which he completed the next month. In the letter, Harris expressed regret about his actions; however, in one of his journal entries dated April 12, he wrote: "Isn't america supposed to be the land of the free? how come, If im free, I cant deprive some fucking dumbshit from his possessions If he leaves them sitting in the front seat of his fucking van in plain sight in the middle of fucking nowhere on a fri-fucking-day night? Natural selection. Fucker should be shot. [sic]".
In December 1998, Harris and Klebold made Hitmen for Hire, a video for a school project in which they swore, yelled at the camera, made violent statements, and acted out shooting and killing students in the hallways of Columbine High School. Both also displayed themes of violence in their creative writing projects; of a Doom-based story written by Harris on January 17, 1999, Harris's teacher said: "Yours is a unique approach and your writing works in a gruesome way — good details and mood setting."
Harris began keeping a journal in April 1998, a short time after the pair was convicted of breaking into a van, for which each received ten months of juvenile intervention counseling and community service in January 1998. They began to formulate plans then, as reflected in their journals.