I'm no psychologist, but I believe there are indicators in Eric's journal that he was actually suicidal. He wasn't as forthcoming as Dylan in his journals about the pain he was in or his endless suffering, but I think this is because Eric knew he was writing for an audience by the time he began writing in his journal... But Eric does mention being picked on, and that he would probably want to pick on himself, too. I think he also mentions that everyone has to die, but they had to die too. A lot of teenage guys don't know how to contend with painful feelings and they can manifest in anger. Then, there's the fact that either one of boys had a year to back out on "NBK" and did not. Personally, their commitment the two had to pulling this off was pretty crazy. Neither really seemed to waiver.