There is a specific manga one-shot titled (sometimes referred to as the movie's "Episode 1" in fan circles) that provides additional backstory:
: Episode 1 is titled "Noman's Land" . It is a reimagined beginning where Meryl (now a journalist) and her partner Roberto find Vash hanging upside down in the desert. Trigun: Badlands Rumble Episode 1
: Nicholas D. Wolfwood rescues Vash by shooting through the floor to create an escape route. There is a specific manga one-shot titled (sometimes
: Episode 1 is titled "The $$60,000,000,000 Man" . It introduces Vash the Stampede as he is pursued by bounty hunters and insurance agents Meryl and Milly in a desert town. Wolfwood rescues Vash by shooting through the floor
: Vash the Stampede intervenes, not to stop the robbery, but to save Gasback’s life during a police ambush.
: A notorious robber named Gasback is carrying out a major bank heist.