My question to the other readers of this book is, why did Captain Beatty want to end his life? Another reason that Beatty wanted to die might have been because he actually did love books and did not want to see them burnt.
Snap out of it!
The majority of people are uninterested in reading or doing anything without instant gratification. He used to be curious about books, just like Montag is. After running away from shock and out of fear that the police will catch him, Guy Montag realizes that when he had the flamethrower pointed at Captain Beatty, he made absolutely no effort to stop Montag or get out of the way of the flames.
Captain Beatty could have seen the books being destroyed by Montag and could not take the pain anymore and wanted to be put out of his misery. We know that most other people in this society are not so happy with their lives.
He even mentions the Greek myth of Icarus. Literature is contradictory. One of the possible answers to this question could be that Captain Beatty suddenly felt extremely guilty because of the fact that he made Guy Montag, his loyal friend and co-worker, burn down his house and destroy the books that he loved.
Contradictions are the whole idea behind literature. Did you notice how his speech is full of Biblical references?