How did Harry know Dumbledore was dead

How did Dumbledore or anyone know that Lily had sacrificed herself for Harry?

Awal Garg

“You all know that the night I lost my strength and my body I tried to kill him. His mother died trying to save him - and unwittingly gave him protection, the I admittedly hadn't foreseen. ... I couldn't touch the boy. "

...

"His mother left him traces of another victim. This is old magic, I should have reminded myself, I was stupid to overlook it. But it doesn't matter. I can touch him now. "

Harry Potter and the Goblet of Fire p.421

We have traces from throughout history that Voldemort is known for overlooking things. At that time he was particularly confident in his strength.

You that at times when I was more powerful than any living wizard, evidence of the immensity of my power had seen?

Harry Potter and the Goblet of Fire p.421

He lived with a wrong interpretation that nobody is smarter than him. So he said:

I knew wizards anywhere would one day be afraid to speak than I became the greatest wizard in the world!

Harry Potter and the Chamber of Secrets p.314

Dumbledore, on the other hand, is careful enough to admire every aspect of the situation and then make a decision. He's really pretty smart. If Voldemort could know it was ancient magic, why not Dumbledore?

Not to mention, Dumbledore didn't come to a decision immediately. He needed time. One of the first appearances of his possible clues was in the first book:

"But why couldn't Quirrell touch me?"

" Your mother died to save you . If there's one thing Voldemort can't understand, it's love. He did not realize that love, as powerful as your mother's for you, leaves its own mark. No scar, no visible sign ... to have been loved so deeply even though the person who loved us is gone will protect us forever. It's in your skin.

Harry Potter and the Philosopher's Stone p.241

So i guess This must be a magic whose popularity is similar to that of a Horcrux. It wasn't very unknown, but it was known only to those who had studied magic extensively. Dumbledore and Voldemort both qualify for this category. The only difference is that Voldemort is ignorant, stupid, idiotic, and overconfident (and of course evil).

It won't be very difficult for him to know. There were other indications as well, see Anthony Grist's answer.

If Dumbledore can determine the location of a Horcrux heavily armed with magical traces, it won't be difficult.

“And did you know that? Did you know - all along? "

I guessed it.But my guesses were usually good "Dumbledore said happily, and they sat in silence for a long time while the creature behind them continued whimpering and trembling."

Harry Potter and the Deathly Hallows p. 593

SQB

Also, your last quote is exactly what my question is. How does Dumbledore know?

Awal Garg

@SQB The part before the last quote should justify how Dumbledore knows : P.

Krumia

This! I think that's the right answer. It is also fairly common knowledge that Avada Kedavra has no counterspell. Everyone would be sure that Voldemort must have used the killing curse (after all, that was the aim of his mission). Dumbledore would have put two and two together and understood that the only way to stop the killing curse is through victim protection.