I just felt like doing a short fanfic drabble - something I haven't done in ages here. So anyway there is massive BotfA spoilers in this, but if you haven't seen the movie now then well yeah. Jeiks. Anyway it's just my take on what might be going on in Fili's head right before he meets his end. I don't know, maybe to make up for what the filmmakers did to the character? Hope you "enjoy."

He didn't look back again at Kili. Not once he knew his little brother wouldn't go chasing after the sound up ahead. A large part of him wanted to go with Kili in the opposite direction. The one that told him that splitting up was the wrong thing to do, but he felt as if he had to. He had no control of the situation. He didn't know where the enemy was, he didn't know what corridor lead to where. All he knew for certain was that he and Kili was alone in the ruins of the tower with something that wanted the whole line of Durin dead.

If they split up at least he could keep their focus on him rather than his brother.

The moment he was alone he felt like a child again. He was terrified and he hated himself for it. He could fight in battles and do good, but then he was in more or less control. Then he knew where to go, where his enemy was and what to do. The lack of control disheartened him. Frightened him. Thorin's last words reminding him of not engaging in fight and he didn't intend to, but he was also sent here to inspect. He couldn't just flee with his tail between his legs.

It didn't take long before the source of the sound showed itself and as Fili made a snap decision to get out of there he was cornered. It was too late. Of course it had been a trap.
Nadadith, I'm sorry. I'm so sorry. He thought frantically as he started down the tunnels again in a last dash to try and get out.
Durins do not flee from a fight...

Then a pale arm moved into his vision and his head snapped back so hard it was a miracle his neck hadn't broken right then. It left the young dwarf dazed, blood seeping from the fresh bruises on his temple as he set to defend himself.
Azog was twice his size and far more vicious than any other foe he had fought before. Because he did fight. He did his best to take the pale orc down or any of the other orcs that were coming too close, but there were just no hope for him anymore.

Then he was disarmed and he felt the tip of Azog's sworded arm dig into his shoulder, going through skin and muscle to render his arm useless. Pressing the small dwarf against the wall Azog grinned at his catch. His victim. His prize.

This is it, Fili thought, set his jaw as he met the defiler's eyes. He knew it was his time to go now and it filled him with dread since the pale orc made no move in actually killing him just yet. It wasn't until he was grabbed by the back of his coat and pulled down the tunnels that an idea of what would happen came to him. The drums causing dust to fall from the cracks in the stone walls.

The worst fear came now though and not because of what was about to happen to him. Seeing his uncle, Dwalin... Even Bilbo down there... It gave him a chance to tell them to go, but where was Kili? Kili was safe right? He sent him away. He had to be safe...

Please be safe.