What events lead up to the final showdown between Beatty and Montag and what causes Montag to pull the trigger?
In Fahrenheit 461 by Ray Bradbury, Guy Montag's wife, Millie turns him in for his books. This leads to Beatty paying Montag a visit and forcing him to burn the books and to burn his own house down. Beatty tells Montag that when he is finished he will be under arrest. As Beatty is talking to him, Faber is also telling him, through an earpiece, to get out of there, and when Montag reacts, Beatty hits him over the head, knocking the earpiece to the ground. Beatty takes the earpiece and when he says, "We'll trace this and drop in on your friend," Montag says, "No," and begins to play with the safety catch on the flame-thrower he still has in his hands. Beatty smiles and says,
"Well that's one way to get an audience. Hold a gun on a man and force him to listen to your speech. Speech away. What'll it be this time? Why don't you belch Shakespeare at me, you fumbling snob? 'There is no terror, Cassius, in your threats, for I am arm'd so strong in honesty that they will pass by me as an idle wind, which I respect not!' How's that? Go ahead now, you second-hand litterateur, pull the trigger."
He takes a step toward Montag, and Montag does exactly that. He pulls the trigger and burns Beatty to a crisp.