Fear.
That's what he felt when he woke to the distressed cries of his own parents.
He charged headlong down the stairs, despondently crying their names. Intrusive sobs, restricting his frantic breaths, invited tears of woe to blur his vision. His senses flooded with an overwhelming sensation of numbness and he could no longer understand the words that escaped his forlorn lips, but the despair in the likely Neanderthal linguistics he felt slither across his tongue was immeasurable. Upon arriving at the scene, anguish stabbed at his heart; it crept up his throat, choking his futile wails. The understanding of the gruesome scene of slaughter that was established before him brought him to his knees.
The malevolent shadow lingering in the corner slipped away into the darkness of the void. The boy rushed to his progenitors, distraught by their state of moribund. Feeling as if he was lying there dying with them, one thought kept echoing in the back of his mind:
Who could have done this?
Neighboring citizens flooded the building; he could tell from the alarmed expressions on their faces that they concluded he was responsible. He refused to heed their horrified gasps. Incapable of anything except weeping, he managed to recognize that from this moment forward his life would be forever changed.