At the beginning of Part 3, "Burning Bright," of Ray Bradbury's Fahrenheit 451, the protagonist, Montag, is taking a grim satisfaction in the process of burning down his own house and its despised television wall with the flamethrower he usually employs to incinerate the books of others. His superior, Beatty, had forced him to do so, taunting him all the while, after Montag's wife Millie had turned him in for keeping a forbidden cache of books.
When Beatty angrily hits Montag, knocking loose the ear piece through which Professor Faber communicates with him, Beatty picks it up and tells Montag he'll trace the device back to its human source. Horrified, Montag yells, "No," and aims the flamethrower at him. Beatty continues to bait the fireman with literary jibes until Montag almost reflexively incinerates him. Soon after, the Mechanical Hound meets the same fate.
Montag falls on the ground, sobbing, and realizes "Beatty wanted to die." His superior sought his own death, and simply goaded Montag into killing him. Despite this realization, Montag continues to cry, and thinks, "He hadn't wanted to kill anyone, not even Beatty." He thinks, "I'm sorry, I'm sorry, oh God, sorry..."