The excerpt provides information about the narration because of the use of the pronoun 'I'.
The First person narrator tells a story from the first person point of view, by using the pronoun 'I'. This narrator is a character involved in the action and participates in the events of the story in some way. It can be a main character in the story or even an observer. Therefore, the information a reader gets from the story in a First person narration is limited to the things the narrator experiences, knows, thinks, or chooses to tell the reader.
Moreover, in the excerpt when it says:
-but with a shudder even more thrilling than before-
The narrator is expressing his own feelings, describing what he or she felt and how it happened. The narrator could not do the same with other characters, because he or she could not feel what another person felt.
