Jeff Kass takes a more straightforward approach in “Columbine: A True Crime Story,” working backward from the events of the fateful day.
The Denver Post

Mr. Cullen insists that the killers enjoyed “far more friends than the average adolescent,” with Harris in particular being a regular Casanova who “on the ultimate high school scorecard . . . outscored much of the football team.” The author’s footnotes do not reveal how he knows this; when I asked him about it while preparing this review, Mr. Cullen said he did not necessarily mean to imply that Harris was sexually active. But what else would such words mean?

“Eric and Dylan never had any girlfriends,” the more sober Mr. Kass writes, and were “probably virgins upon death.”
Wall Street Journal