WARNING: The following contains major spoilers for Before the Batman: An Original Movie Novel, on sale now.
In the Batman Universe, it's safe to say the deaths of Thomas and Martha Wayne inspired Bruce Wayne to become the Bat. It's been seen across many comics, films, cartoons, animated movies, games and novels, motivating Bruce to clean up Gotham by waging war on the criminals that broke his family.
However, in the prequel novel to Matt Reeves' The Batman, titled Before the Batman: An Original Movie Novel, it's revealed that the Waynes being gunned down in Crime Alley didn't create the Caped Crusader; someone else sparked the idea.
This book from David Lewman had Bruce not being bogged down by his parents' deaths when he was ten. Instead, he kept moving around the world in his teens to preoccupy his mind, learning various science disciplines, as well as martial arts to test his true potential.
When he returned home to Gotham City, Bruce used the cave beneath Wayne Tower as his base, fixing up a muscle car he found from the '60s or '70s. He loved these pet projects, even going so far as to collect goop and gum off the streets to dissect their properties with his chemistry expertise. It was all due to him being restless and a socially awkward person without friends -- something that worried Alfred.
In time, Bruce became a street-racer to sate his need for speed, but in one race, he spotted a flare just before the engine of another racer, Dex, exploded. She crashed, but rather than finish the race, Bruce pulled his car over, broke the glass and got her out before she blew up. Dex was thankful for it, albeit Bruce was going under the moniker of Paul -- a disguise because he hated people recognizing him for his true identity. Bruce soon realized saving someone was the adrenaline rush he needed, which speeding late at night would never provide. It helped that he also had a crush on Dex and was able to save her.
The Wayne heir then decided to step up his detective game, sprucing up the car, making weapons and even using his company to secretly attain materials for armor. What further inspired him was how he remembered getting pulled over by cops as a teen, only to be let go as they knew paying this ticket would be chump change. In addition, they didn't want to mess with Gotham's elite.
He reconciled this privilege and corruption, wanting to do more for the city, which is what Thomas planned as mayor before the tragic night. Bruce's big test came when he tripped up a mugger in the street, caught the items lifted and gave it back to the owner before secreting out just when she was about to make him out as a celebrity. All these things made him realize that as a vigilante in the night, he could become someone else, help people and attain the thrill-seeking life he desperately craved.
The Batman hits theaters on March 4 before making its way to HBO Max on April 19.