As the raven-haired man arrived on the the Tower, he made his way up the stairs and past the dark wizards, the Death Eaters, waiting there, his eyes dark and unreadable. He turns to face the Headmaster, who stands on the tower looking shook.

"No." Severus' deep, baritone voice came, breaking the moment between Draco and Albus, the young man's wand was leveled at the old wizard.

A long few moments passed of the older professors just staring at each other, Severus finding himself unable to say anything. It's the old man that speaks.

"Severus...please." the aged wizard said softly, practically staring into Severus' soul. The man doesn't respond. How can he respond to that? A brief flicker of something unreadable crossed his face before he finally speaks...but not the words anyone expected to hear from him, least of all the Headmaster himself.

Severus draws his wand, taking a sharp breath, making a choice that would change everything. A flash of blue from a spell usually green changes everything- making a mark on the school not easily forgotten. The Killing Curse.