Trayvon Martin grabbed his killer’s gun just moments before he died and uttered a profanity-laced threat. In a desperate life-or-death struggle, George Zimmerman clutched Trayvon’s wrist, broke his grip on the semi-automatic firearm and shot him once in the chest.

That account appears in a new book written by Zimmerman’s best friend and confidante.

There’s just one problem: Zimmerman never said that to the police.

Now the book, Defending Our Friend: The Most Hated Man in America, and author Mark Osterman’s two television interviews have landed on the prosecution evidence list, as more versions of Zimmerman’s story emerge. A man who wrote a book calling Zimmerman “the kindest and most sincere” person will wind up in court — for the prosecution, experts agree.

“It was emotionally draining for George as he relived that awful moment when he managed to control the gun, then fired out of fear for his life,” Osterman wrote.

Osterman, U.S. air marshal who lives in a Central Florida, was among the first people Zimmerman’s wife called on Feb. 26 when she learned her husband had just shot someone. Osterman rushed to the scene that night, and accompanied his best friend every step of the way through the investigation, including his first three interrogations by Sanford police.

Osterman acknowledges that former Sanford Police Chief Bill Lee was his one-time lieutenant in the Seminole County Sheriff’s Department whom he held up as a father figure. Osterman says he was quickly recognized by cops on the scene, but insists he never coached his friend on what to tell them after the death of Trayvon, an unarmed Miami Gardens teenager.

Afraid for the Zimmermans’ safety, Osterman took the couple in from the very first night of the shooting. His 172-page book describes how Zimmerman told the story of the killing over and over again until he was physically drained. When he told it to police, Osterman said, Zimmerman threw up.

But Osterman’s account is a sharp deviation from the versions Zimmerman gave, which experts say will undoubtedly be used to try to impeach the defendant’s credibility and cast doubt on his claim of self-defense if each telling changed or was embellished.

“I desperately got both of my hands around the guy’s one wrist and took his hand off my mouth long enough for me to shout again for help,” Osterman quotes Zimmerman as saying.

“For a brief moment I had control of the wrist, but I knew when he felt the sidearm at my waist with his leg. He took his hand that was covering my nose and went for the gun, saying, “You’re gonna die now, motherf-----.’ Somehow, I broke his grip on the gun where the guy grabbed it between the rear sight and the hammer. I got the gun in my hand, raised it toward the guy’s chest and pulled the trigger.”

DNA reports released Wednesday showed there was no DNA from Trayvon on the gun.

Even as Zimmerman himself offered slight variations of where Trayvon first appeared or from what direction, none of his written or recorded interviews with police suggested a battle over the firearm. He told police that when he wriggled off the concrete onto the grass, his gun was exposed, and Trayvon reached for it.

In the version Zimmerman’s brother Robert told CNN, Trayvon said something like, “You have a piece? You die tonight.”