Three days after George Zimmerman killed an unarmed teenager and went home free, he had a predicament: The lead detectives investigating the shooting seemed to no longer believe his story.

Sanford Police Det. Chris Serino told Zimmerman in a series of interviews that day that he was a “good guy,” but that there were holes in his story, including minor injuries that did not match the beating he said he received at the hands of a “child” who carried candy.

Zimmerman repeatedly told police that Trayvon Martin sucker-punched him, tried to suffocate him and bashed his head into the concrete to the point it felt his “head was going to explode.” He said Trayvon tried to take his gun from him before saying: “You’re going to die tonight, motherf-----.”

But Serino wondered why Zimmerman’s skull wasn’t fractured, why he didn’t know the street names of a tiny neighborhood where he’d lived for three years and why he had no defensive wounds on his hands. Serino got him to acknowledge what Trayvon’s parents and lawyers have said all along: that Zimmerman got out of his car that night not so much to check for an address to give police, but to find out where the teen went.

“That was a kid with a future, a kid with folks that care. Not a goon,” Serino said. “In his mind’s eye, he perceived you as a threat. He has every right to defend himself.”

Tapes released Thursday of questioning between Zimmerman and Sanford police underscore a sharp contrast between the public statements made by the Sanford Police Department the weeks following Trayvon’s killing and the conversations that went on internally. They offer the first glimpse of a man who told detectives that he takes medication for attention deficit hyperactivity disorder, and who at one point became the most controversial man in America. The interrogations also reveal that detectives were troubled by a man with a history of inserting himself into law enforcement matters who did not have the training to determine what a “suspicious” person should look like.

Zimmerman detailed a harrowing night when he said a stranger accosted him for no reason and allegedly threatened to kill him. At least twice witnesses failed to come to his aid. One of the first things Zimmerman said to Det. Doris Singleton: The bad guys always get away.

Hinting that Zimmerman had left something out of his account, Serino asked over and over why Trayvon would have been so enraged as to deck a perfect stranger. Zimmerman, he suggested, had chased him.

“You wanted to catch him. You wanted to catch the bad guy, the f-----g punk who can’t get away,” Serino said, referring to words Zimmerman used on his call to police.

At one point, Zimmerman answered: “I wasn’t following him; I was just going in the same direction he was.”

Serino retorted: “That’s following.”

Zimmerman is facing a second-degree murder charge for the killing. The arrest came six weeks after the shooting and a short time after a widely criticized investigation was handed over to other agencies. Despite Serino’s misgivings — and the detective’s recommendation that Zimmerman be charged with manslaughter — Sanford Police publicly stated that there was no probable cause to make an arrest, so the politically charged case was handed over to the Florida Department of Law Enforcement.