Lyric discussion by MisterMarcus 

I think it's much darker than what most people here interpret it. I think this person is a stalker/obsessive, who literally has murdered this girls' boyfriend because he wants her for himself.

"So sick of the taste of blood", "I won't ask your God for mercy...my soul is dirty" suggest that he's gone well beyond mere thoughts and into action.

"I'll write your girl a letter, it'll make everything better", he'll tell the girl that they can be together now that her boyfriend is out of the way. Classic creepy horrifying stalker stuff.

Plus the lyrics and general vibe of the chorus...."we should be together, it's our destiny, so whatever I do is justified"

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