He is best known for writing the scripts for Gangster Squad (2013) and the DC Extended Universe films Aquaman (2018) and Zack Snyder's Justice League (2021), and for developing the police TV series Training Day and Deputy, which were canceled after a single season.
Beall launched his writing career in 2006 with the publication of his acclaimed first novel LA REX, after working for 10 years as a homicide detective and gang investigator with the Los Angeles Police Department.
Beall adapted the book for Oscar-winning producer Scott Rudin and the script was featured atop The Black List, Hollywood's annual survey of the industry's favorite screenplays.
Much of the second act of Beall's original Justice League script took place in a post-apocalyptic earth where Darkseid had manipulated Superman and then used the Kryptonian to conquer the world.
The surviving members of the Justice League had to join forces with villains from the DC Universe in order to defeat Darkseid by sending Flash back in time to warn Batman prior to the invasion.