Also in the first book, Harry thinks to himself that Snape might be able to read minds. Four books later, we learned that Snape was a Legilimens.

Harry and Ron were distrustful of Snape from the start. Warner Bros.

While fretting over whether or not Snape knew he, Ron, and Hermione had discovered who Nicolas Flamel was, Harry thinks to himself that Snape "could read minds."

Later, in "Order of the Phoenix," Rowling reveals that Snape is an accomplished Legilimens, meaning he sort of can read minds. Here's how Snape describes Legilimency to Harry:

"Only Muggles talk of 'mind reading.' The mind is not a book, to be opened at will and examined at leisure. Thoughts are not etched on the inside of skulls, to be perused by any invader [...] Those who have mastered Legilimency are able, under certain conditions, to delve into the minds of their victims and to interpret their findings correctly."