When Jasper (Austin Amelio), a crooked cop, is pulled out of the sting operation, Johnson takes over as the fake hitman. He excels, and the police ask him to become their phoney hitman permanently.

In 2001, Texas Monthly staff writer Skip Hollandsworth wrote a feature article about Johnson, his double life and his success as a fake hitman – a role he played for 30 years, starting in 1989.

Screenwriters have been trying to turn the story into a film since 2001, but none have succeeded – until now.

Hit Man director Richard Linklater and Powell co-wrote the story, focusing on Johnson’s relationship with a woman he tries to capture in a sting operation.

Linklater told Texas Monthly in May that the producers spent US$10 million or US$11 million (he doesn’t know for sure) to produce the film independently. Last year, Netflix bought Hit Man for US$20 million to stream on its platform.

Here’s what to know about the ending and how it differs from the true story.

(Warning: Major spoilers ahead.)

In Hit Man, Gary Johnson and Madison get away with murder and raise a family together

In the middle of the film, Johnson, using the undercover name Ron, meets Madison, a scared young woman who wants to murder her husband to escape their abusive relationship.

Johnson, who is attracted to Madison and empathises with her, persuades her to divorce her husband and run away. A couple of weeks later, Madison and Johnson, still pretending to be Ron, meet again and begin dating.

While they are hanging out, Johnson accidentally teaches Madison how to kill her husband and get away with it. He then discovers that the husband is trying to kill Madison and tells her. Madison kills the husband and uses Johnson’s advice to hide the body in a poor neighbourhood.

Johnson learns of the murder and reveals his real identity to Madison, causing a big fight. However, they are forced to overcome their hurt feelings so they can work together to stop the police from discovering the truth.

They fool everyone but Jasper, who has been following Johnson and Madison for weeks. Jasper attempts to blackmail them, but Madison spikes his drink, and Johnson suffocates him after he passes out.

The next scene flashes forward to a time years later when Johnson and Madison are married and raising two children.

The real Gary Johnson didn’t murder anyone – or marry Madison

Though Hit Man recreates many moments from the Texas Monthly story, the second half of the movie is mostly untrue.

Madison was created for the movie, and though the real Johnson did marry and get divorced three times, there aren’t any reports on whether he had children.

Madison appears to be loosely based on a section of the Texas Monthly article where Johnson refers a young woman to social services and a therapist instead of getting her arrested.

Hollandsworth wrote that the woman wanted to hire a hit man because her boyfriend was abusing her.

“Before Johnson contacted her, he did some research into her case,” Hollandsworth wrote. “He learned that she really was the victim of abuse, regularly battered by her boyfriend, too terrified to leave him because of her fear of what he might do if he found her.”

Powell said in the press notes for Hit Man that this moment helped him and Linklater figure out how to tell Johnson’s story.

“He looked at this person and thought, ‘This is a victim of their circumstances, and I want to help them through this thing,’” Powell said. “A guy who imitated humanity was in turn finding his own humanity. That relationship turned out to be key to the entire movie.”

Per UPI, Linklater told a Hit Man press conference that Powell was the first to suggest that they should “deviate” from the true story.

“Glen kind of loosened the log jam I was in,” Linklater said. “Once that floodgate opened, we were off to the races. We just started having these great ideas.”

Gary Johnson is a hybrid of his two personas at the end of the film

A major theme in Hit Man is identity and whether it is possible for someone to change.

This is important particularly to Johnson, as he becomes more like Ron the longer he dates Madison.

In May, Powell told Today that Johnson becomes a “hybrid” of both personalities at the end.

“It’s not too late to seize the identity that you want for yourself and chase what makes you happiest,” Powell said of the movie’s message. “If you feel like you’re stuck in life, if you feel like you’re stuck in an identity that’s not making you happy, just make the choice to change.”