Kill or be killed.
He had thought about those four words many times, and he had come to the conclusion that truer words had never been said.
Kill or be killed; figuratively or literally.
But everything changed.
During his lifetime, he had lost many people, like his paternal grandfather. Condolences were offered to him. He, too, offered his condolences, he told his father that he was sorry for his loss. Of course, he had only said it out of courtesy. But when Tommy died, he finally understood what sorry tasted like, what loss felt like. He lived it. He lived with it every single day. Tommy was his brother, his best friend. And all that remained of him now was a sad emptiness. Oliver found it odd how someone who doesn't exist can fill up so much space.
So he did the only thing he knew to be right. He promised his fallen brother that he wouldn't be the murderer Tommy believed him to be. He fought desperately against himself, his demons, his belief, and his true nature. He let himself hope it was all possible, he pretended that those four words weren't true, and for some time it had worked out.
But everything changed.
Oliver remembers telling Digg with confidence that they would protect Felicity, when she had agreed to help them find Walter. And he meant it. Because he needed her expertise. He was well aware of the danger she would be exposed to, but he was also that selfish.
But everything changed.
He thinks about what happened earlier that night. Images flash in his memory, of Felicity being tied up and scared, of the Count holding the syringe to Felicity's neck, of the Count with three arrows in him.
He had to kill him. The Count knew about his alter ego, he had hurt John, he was going to hurt Felicity too and he wasn't going to stop there. It was very simple; kill or be killed. Because no matter what, Oliver was one step behind; even though the Count's fire had missed him, he would still kill Oliver by hurting Felicity.
He had to put arrows in him.