When Eric Harris exchanges gunfire with Neil Gardner near the start of the rampage, bookshelves can be seen in the background, indicating Harris is in the library, when he had not reached it yet.
Neil Gardener was a county sheriff's deputy, but he's depicted as a Colorado state trooper in the episode.
Neil Gardener had a mustache at the time of the attack but he's depicted as being clean shaven in the episode.
In real life, the model of carbine Eric used in the attack was a Hi Point 995. In the documentary however, the model of carbine he is using is shown to be a Kel-Tec Sub 2000.
Daniel Rohrbough is depicted as being killed instantly by Eric Harris, when he was actually wounded and fatally shot in the back by Klebold seconds later as the shooter descended the stairs to check on the bombs in the cafeteria.
Eric Harris is shown shooting Rachel Scott with a shotgun. However, he shot Scott with a Hi-Point 995 in real life.