How is flowers for algernon a tragedy?

The reason Flowers for Algernon is a tragic is because a grown man whos mentally challenged becomes best friends with Algernon- the mouse. Since they both had the same operation done, whatever the mouse did, Charlie ends up doing. Also, since Algernon dies in the end of the book, the author leaves you predicting that Charlie will die too. The book also tells that most of Charlie's "Friends" end up laughing at the man.