Shadow of a Doubt, Young Charlie realizes that Uncle Charlie is a killer from what source?

There are hundreds of films about this topic but none do it as well except for David Lynch (who was definitely very influenced by this film). I think the main theme of Shadow of a Doubt is the loss of innocence.

So much has been written about Vertigo's themes of obsession, loss, regret, illusions, power, and delusions but I don't see Shadow of a Doubt analyzed on the level it deserves. His other masterpieces Psycho and Rear Window go a little further in developing meaning and complex characters (and Marnie but I think that was a bit of a failure) but Vertigo and Shadow of a Doubt are on another level. I also think these 2 films have a much deeper meaning and subtext than the rest of his work. His characters are usually cool and have fun dialogue but only in Vertigo and Shadow of a Doubt does he put the importance of the characters above the plot itself. Hitchcock is one of the greatest directors ever but my main problem with him is that he usually puts suspense and an intricate plot above characters. Personally, I would only put Vertigo above it.

In my opinion, Shadow of a Doubt is one of Hitchcock's greatest films.

Shadow of a Doubt, Young Charlie realizes that Uncle Charlie is a killer from what source?