One of George Zimmerman's former colleagues at CarMax, where he worked in 2008, complained formally about the man who killed Florida teen Trayvon Martin, alleging serial hazing that lasted for months and included pranks and ethnic jokes.

When the salesman complained to management, Zimmermandenied the harassment.

"The guy was so convincing when he was confronted by management to the point where I doubted my own self. I would not be surprised if he got away with it [Martin murder accusation]."

"He's got, like you say, a good poker face. Great poker face," said the colleague. "That pretty much summarizes this guy's personality. Great poker face."

The employee, who is an Arab-American, worked part time at the used car retailership during 2008, and rose quickly to become one of the company's top salesmen, despite the hazing, he says.

"These are some of the bully activities I have been facing that led me to be concerned about my work environment," he wrote in the one page complaint. The complaint accused Zimmerman of pressuring him to split deals with him, of repeatedly "impersonating me in a terrorist character," and mocked him constantly to earn the laughs of fellow workers.

In the letter, the colleague states, "Since I started working in CarMax Sanford, George has been dealing with me in an unprofessional manner and have mastered the art of emerging as the nice guy to others in order to make me look like the unsocial type and out of place."

The former car salesman insists that Zimmerman, who was 24 at the time, was not a racist, but would do anything to gain the approval of his colleagues, chiefly harassing their new colleague with Middle Eastern jokes. He said the racist remarks hurt more than anything else.

Speaking exclusively to ABC News, the man said, "He wasn't joking around. He was choosing his words. He was making fun of my accent, or pretending that I have a thick accent."

Zimmerman's former colleague asked that his identity not be revealed because he feared any association with the Zimmerman trial could jeopardize his family's security.

He also recounted first hearing Zimmerman's name in the media, "Because that name, I'll never forget... I had to pull over when I heard him on the news."

The former colleague says that Zimmerman, who is now 28, referred to him as "a f---ing moron" on countless occasions, despite his recognition from his superiors as a talented salesman.

The man said he wanted to do his work and go home, "But Zimmerman noticed the gap, or the unwelcome from some of the other employees, and he took that opportunity to pretty much put me as a target, and to make fun of me, bully me around, pretty much harass me 24/7. Just make it difficult for me to work there."

He says the bullying was noticed at CarMax. "Other sales people would come and approach me and say, don't worry about this guy, he's a bully, he's an idiot, he's young, he doesn't know what he's doing."

The former colleague said others at CarMax said Zimmerman was upset for not getting the promotion he thought he deserved, and that's why he took out his frustration on the colleague.

Zimmerman's attorney would not comment on the story. CarMax issued a statement saying it did check that matter, but that "CarMax does not provide information on internal human resources matters."

Other employees told ABC News they recall the two, and remember Zimmerman as a "prankster, a jokester," at work.

Zimmerman was let go shortly after the complaint was lodged, apparently on an unrelated matter.

These accusations come a day after a report by Chris Serino, the lead homicide investigator in the shooting death of Trayvon Martin, was made public. Serino's report expressed strong skepticism of Zimmerman's account of the shooting, describing Zimmerman's injuries as "marginally consistent with a life threatening violent encounter."

The detective also questioned Zimmerman's account of being afraid of Martin, who was 17 and unarmed when he was killed on Feb. 26.

Serino's report is the latest in the see-saw of information released alternately by the state and the defense, with chunks of it seemingly damning for Zimmerman, while other parts appear to support his claim of shooting Martin in self defense.