He did not know why he was doing it, why he was approaching the dying man: He did not know what he felt as he saw Snape’s white face, and the fingers trying to staunch the bloody wound at his neck. Harry took off the Invisibility Cloak and looked down upon the man he hated, whose widening black eyes found Harry as he tried to speak. Harry bent over him, and Snape seized the front of his robes and pulled him close.
A terrible rasping, gurgling noise issued from Snape’s throat.
“Take . . . it. . . . Take . . . it. . . .”
Something more than blood was leaking from Snape. Silvery blue, neither gas nor liquid, it gushed from his mouth and his ears and his eyes, and Harry knew what it was, but did not know what to do —
A flask, conjured from thin air, was thrust into his shaking hands by Hermione. Harry lifted the silvery substance into it with his wand. When the flask was full to the brim, and Snape looked as though there was no blood left in him, his grip on Harry’s robes slackened.
“Look . . . at . . . me. . . .” he whispered.
The green eyes found the black, but after a second, something in the depths of the dark pair seemed to vanish, leaving them fixed, blank, and empty. The hand holding Harry thudded to the floor, and Snape moved no more.
Harry Potter and the Deathly Hallows – J.K. Rowling