Although he learned street smarts to adapt to the rough area, he joined the military to escape the harsh life he found there. Dropping out of high school, Ayer became a top sonar man for the U.S. Navy, stationed aboard a nuclear attack submarine during the last days of the Cold War. After being honorably discharged, he returned to Los Angeles, taking on jobs as an electrician and in construction while writing short stories in his spare time. In the early 1990s he met A-list screenwriter Wesley Strick while working construction on Strick's home, and Strick convinced Ayer to write a screenplay based on his experiences in the Navy-Strick also pointed him to Syd Field's book Screenwriting and provided many scripts for Ayer to study as he learned the form. After many attempts to create a script he thought producers would buy, Ayer—then living again near the Rampart District—decided to write something personal, building on an earlier short story he had penned.
By 1995 the story had evolved into the screenplay "Training Day," following the exploits of a intensely corrupt African American detective and his new rookie protégé and trying to capture modern Los Angeles' little-depicted gritty side. The script earned Ayer an agent and the attention of Hollywood, but was not made. Instead the strength of the script couple with his Naval experience earned him a rewrite job on the WWII submarine thriller "U-571"-although director Jonathan Mostow had already decided to hire him before learning of his background as a submariner. Ayer followed up the well-received film with a script-doctoring stint on a street-racing film called "Redline," which evolved into the surprise hit "The Fast and the Furious" (2001).
By then, revelations of real-life police corruption in the Rampart district had made headlines and Ayers calling-card script "Training Day" began to glow red-hot, going into production under director Antoine Fuqua with Denzel Washington in the lead role and Ethan Hawk as his partner. Upon its release in 2001, "Training Day" earned critical accolades for its ferocious, untamed look at the harsh side of law enforcement in the urban jungle (despite a too-conventional thriller ending) and resulted in an Oscar nomination for Hawk and an Academy Award win for Washington.
Ayer's next project was equally edgy, teaming him with novelist and L.A. noir maestro James Ellroy ("L.A. Confidential"), who wrote the original story for "Dark Blue" (2003) which Ayer developed into a screenplay for director Ron Shelton. The story also focused on a corrupt LAPD officer (Kurt Russell) and his rookie partner (Scott Speedman) who become caught up in a tangled web of politics, personal emotions and misguided justice at the flashpoint of the 1992 Los Angeles riots. Starting strong with vivid character and seemingly complex plots, the movie ultimately unraveled with another unfulfilling ending, but acutely demonstrated Ayer's ability to create vivid dialogue and morally ambiguous characters who are nevertheless sympathetic.
Ayer next penned the script for “S.W.A.T.” (2004), a tense cop thriller that focused on a disgraced SWAT team member (Colin Farrell) given a second chance when an expert commander (Samuel L. Jackson) recruits and trains a top-notch five-person team that faces trouble with its first assignment—escorting a drug kingpin (Oliver Martinez) offering $100 million to anyone who can help him escape. The scribe then made his directorial debut with “Harsh Times” (2006), a haunting character study about a Gulf War veteran (Christian Bale) coming home from war to find it nearly impossible to get his life back on track. With his old childhood buddy (Freddy Rodriguez) by his side, the war veteran goes on a violent rampage through South Central Los Angeles, while his hopes of making the LAPD slips through the cracks. Using “Taxi Driver” (1976) as an obvious model, Ayer nonetheless crafted a compelling tale about the loyalty and the inability to leave the past behind.