Dylan's mindset

One thing that I wonder about Dylan is that I think he had some sort of spiritual beliefs in some sort of capacity. I read another topic about his eastern philosophy influences. In his writings, we see that he believes he will go somewhere better when he dies and seems to believe in some sort of afterlife. He even says in the final tape on the day of the massacre that he know he will be happier wherever he goes. This mindset confuses me so much because if he was spiritual, how on Earth could he believe that doing something so horrible as his final act on this planet would give him any sort of positive afterlife? I can't think of any religion or belief system that rewards a person with a happy afterlife when they have done horrible things, and I doubt many people would deny that murdering a bunch of innocent people, let alone kids, would not be considered horrible. Was it his mental illness issues that caused him to be blind to this sort of spiritual logic? That probably seems like an oxymoron to some people "spiritual logic" but if he did hold spiritual beliefs in any capacity, why would he think he would get a good afterlife or be happier wherever he went after his death?
Eric didn't seem to be religious or spiritual, at least not openly. It doesn't seem like he had this same gap in "logic" as Dylan did.

Any thoughts on this or any insight on a type of spiritualism that rewards bad behavior that might have allowed Dylan to support this kind of thinking?

There's one spiritual mindset (I don't think it has a name -- loosely based on New Age-y stuff at the very least) that speaks of everyone on Earth having a purpose. Some people have purposes like raising children, taking care of the elderly, influencing people through their political/pop culture fame, etc. Other people, and Dylan would be a part of this group, have a purpose that makes them commit to something horrible for the betterment of humanity. Events like Columbine are catalysts for something bigger in this regard: an event that impacts an entire generation and transforms the world around it for both better and worse. The souls of those involved in committing this sort of act are 'safe' from an awful afterlife for as long as they keep exactly to the letter of their agreement in such. (In other words, the minute they kill more than was agreed on or change anything else about the event.. they're in deep trouble.) Some actually say that the souls prepared to do such a thing in the first place are old souls who've been around a long time and whose good acts in the past counterbalance their heinous act of this one lifetime. It's not to say that the soul itself won't struggle with it, but the afterlife for these souls will be as good as it is for any one of us just living their lives in peace.

Maybe Dylan justified what he was about to do in the same way. Maybe he did feel like this was his purpose in life and that he would simply transition into the afterlife without suffering greatly. Perhaps it was also so that he was in enough deep agony that he was unable to see how this agony could possibly become worse in the afterlife. Perhaps he believed that all of what he had done would be washed away the minute he entered the realm he so longed to see (again?). I suspect that Dylan felt so out of place on this Earth that he created a new 'home' for himself in whatever would come for him after death, and that this home would be happier and more loving than anything he'd experienced down here. Perhaps it was an illusion, who knows, but it was one that gave him great comfort. We mustn't also discount the 'godlike' self he fashioned for himself in this matter. The god among mortals was leaving this planet after teaching the lowly humans a painful lesson. Nothing can touch a god, right? The normal rules don't apply to them. If he believed this, then I would definitely say that the delusions accompanying his mental illness had a stronger hold on him than any amount of spiritual logic did.

His mindset was to go and kill people on that day.

He just wanted to be dead, he thought any place other than earth would be a lot better for him. That was his mindset.

On the one hand he just wanted to die, to no longer be in the fight with himself (in a depression), on the other hand he could realistically imagine (wanted to believe) that his life is actually test that all is unreal and his fate is to pass this test with a "zombie", proving its higher purpose, allowing fate to guide him. And since this test, in the end it's a reward, not a punishment. In fact, his desire to die was so strong that the rest does not really matter.

Frankly, I think that the only way Dylan could have saved himself from the world would have been realizing that society (especially ignorant people) is not going to change after your wake up call to raise people from their zombified brain state. History itself shows that there always have been around the mindless flock and the talented (and suffering) ones.
Killing yourself and other innocent people does not change things even in front of a worldwide audience. Centuries have passed from the first time that blood was shed on the behalf of every ideology ever conceivable and we're still at a starting point. Nobody learns, nobody is willing to change for the better. But if you manage to stay alive despite everything else, you will set a more constructive example for those around you who might get inspired (and not just enraged, vengeful and bloodthirst).
On another note, I don't understand what 'spirituality' means. It's just a bleak word. All we're searching for is something that makes us happy or peaceful about our state of mind, at least for a while. If it means to be in touch with our inner selves, that's psychology. A deeper knowledge of our nature. Looks more like science and the endless search for the complete understanding of how our mind works.