Pursuant to my question here, asking why Harry couldn't see Thestrals immediately following Cedric Diggory's death, now I want to know why Harry could see Thestrals, as a re-read of canon shows that Harry actually did NOT see Cedric get killed. He had covered his face and eyes with his hands and his eyes were closed as Cedric was killed.
And then, without warning, Harry’s scar exploded with pain. It was agony such as he had never felt in all his life; his wand slipped from his fingers as he put his hands over his face; his knees buckled; he was on the ground and he could see nothing at all, his head was about to split open. From far away, above his head, he heard a high, cold voice say, ‘Kill the spare.’
A swishing noise and a second voice, which screeched the words to the night: ‘Avada Kedavra!’
A blast of green light blazed through Harry’s eyelids, and he heard something heavy fall to the ground beside him; the pain in his scar reached such a pitch that he retched, and then it diminished; terrified of what he was about to see, he opened his stinging eyes.
Goblet of Fire - Page 553 - British Hardcover
‘Righ’, now, who can tell me why some o’ yeh can see ’em an’ some can’t?’
Hermione raised her hand.
‘Go on then,’ said Hagrid, beaming at her.
‘The only people who can see Thestrals,’ she said, ‘are people who have seen death.’
‘Tha’s exactly right,’ said Hagrid solemnly.
Order of the Phoenix - Page 394 - British Hardcover
According to the above passages, Harry technically did not see Cedric get killed, but witnessing a death is required for seeing Thestrals. So how is it that Harry was able to see Thestrals?