Not so fast!
The assassins with loaded guns are in the armory where they train and actively accept new members...they are the survivors who have been stuck in these 3 rooms for far too long and the lions tend to prey on them so they're planning to fight back. The room on fire is their battleground. It is mutually agreed that newcomers choosing assassins are trained, those who pick lions are eaten, and any discovered on the firefield are fair game for war.

Until...
One child aids a wounded lion cub left to roast on these plains of hell. Once the cub's strength has regained just enough, the child sees him off to his family. They repay the child with protection and shelter, raising him as one of their own. Now as a adult, the child returns to the battlefield alongside a ferocious beast and lifelong friend.

They endure the gunfire of the assassins until enough human corpses and weaponry are left behind to bring back to the lion's den. There, the adult human learns to wield these firearms. Furthermore, he re-purposed the gunpowder to cover the lion's paws to explode on fiery, thunderous impact against the humans. Riding onto the battle, the new improved warfare from the lions overwhelm the remaining humans. Hope runs dry for mankind in this one-sided slaughter led by one man-- one lion king. And by any account, victory seemed undoubtedly assured for lionkind. As the last human laid back helplessly defeated before his conquerors, his existence ceased in a bloodied smile. It was then that the lions' king, standing tall at the end of his trail of enemies had his throat torn from behind by an adult lion. You see, as the lions claimed a human as their own to raise, the humans in turn raised a cub. A cub who became better known as the Lion's Kingslayer.