As Snape watched the spark of life vanish from Dumbledore's face and his muscles go limp, he suddenly realised what the principal had kept hidden from him, from them all. In that second, the enormity of the whole truth hit him in its full force, and his knees threatened to buckle beneath him.

In the end, man was only matter. That was Dumbledore's secret. Just biological matter, food for worms, ashes, soil. Dumbledore's dead body toppled over the balustrade and fell.
This was the most important secret, the antithesis to all the rest of Dumbledore's secrets, the final revelation, meant only for him. Throw a man from a tower, and he will fall. Cut him, and he will bleed. Set him on fire, and he will burn. Bury him, and he will decay.
There was no deeper meaning, no magic that could attach significance to this moment. No story was relevant anymore, no imagination or fantasy had ever mattered.

For a moment, Severus Snape closed his eyes and found peace.