system
Given the following post, respond as if you're commenting on Reddit:
human
[harry potter] How did everyone know that it was Voldemort, himself, that killed Lily and James Potter?

 And why were they so sure that Voldemort was gone? I'll admit, I haven't read the books in years, so there may be something I'm forgetting, but wasn't his body destroyed when he tried to kill Harry? It seems like a huge leap of faith to just assume he was the one, and that he was killed that night, when there wasn't any evidence. It could very well have been one of his death eaters. Plus, I doubt that his death eaters would be very quick to reveal the fact that he had been destroyed. He was feared so much, even his name is considered frightening. So, it doesn't make sense to tell people he had been destroyed, because even the idea of him would be enough to instill fear, and it would ensure that they stay on top.  And why were they so sure that Voldemort was gone? I'll admit, I haven't read the books in years, so there may be something I'm forgetting, but wasn't his body destroyed when he tried to kill Harry? It seems like a huge leap of faith to just assume he was the one, and that he was killed that night, when there wasn't any evidence. It could very well have been one of his death eaters. Plus, I doubt that his death eaters would be very quick to reveal the fact that he had been destroyed. He was feared so much, even his name is considered frightening. So, it doesn't make sense to tell people he had been destroyed, because even the idea of him would be enough to instill fear, and it would ensure that they stay on top.
gpt
Well, the fact that he went missing afterwards, and a bunch of his death eaters came forward and said he had imperius'd them, but was gone now, was enough for most people. 

And the reason *they* came forward and said that is because... he *was* gone. And frankly, without him, they stood very little chance against their enemies. Not a single one of them wanted to go 1v1 with Dumbledore. 

Or 1v3. 

1v5 was still pushing it. 

Their invincible dark lord was just *gone*, and this child had survived him. Some of them thought Harry might be the *new* dark lord, in time, and wanted to wait and see. Others went out a-torturing in vengeance, and got captured. 

But as for how people *initially* knew... Dumbledore told them. He knew Voldemort would want to personally kill the child named in the prophecy. And he knew that, though James and Lily had died, Harry had survived. Something Voldemort would not have allowed. And he knew what had happened to him - his own killing curse, rebounded by Lily's protection, amplified to the point where it destroyed the house and obliterated him. 

So, Dumbledore knew. And he told people.