Neighborhood watch gunman GEORGE ZIMMERMAN – who ignited a national furor when he shot and killed Flor­ida teen TRAYVON MARTIN  – is a hot-headed bully with a crim­inal past, The ENQUIRER has learned.

THE ENQUIRER launched a special in­vestigation to uncover the real story behind the tragedy that’s rocked America and discovered the teen’s killer has had repeated run-ins with the law. He was even charged with “resisting an officer.”

What’s more, we spoke with two eyewitnesses who told us what happened on the fateful evening of Feb. 26, when the 17-year-old was heartlessly gunned down by Zimmer­man while walking in a gated Sanford, Fla., community.

The ENQUIRER obtained shocking court documents showing that Zimmerman has a long, checkered history of violence, including domes­tic disputes with a former fiancee who turned to the courts for help.

Zimmerman’s ex-fiancee, Veronica Zuazo of Orlando, petitioned an Orange Coun­ty, Fla., court in 2005 for an injunction of protection, claiming that on at least three occasions Zimmerman’s unpredictable temper led to violent physical outbursts.

In one incident, Zuazo says Zimmerman was upset after she arrived home later than usual.

“He was sexually groping me and said he could be­cause Iwas his woman,” she charged in a statement to the court.

“I told him no, to leave me alone. He picked me up and threw me on the bed.”

A frightened Zuazo says Zimmerman finally left after she smacked him.

And in July 2005, the thug was arrested on felony charges of resisting an offi­cer with violence and battery on a law enforcement officer during an altercation at an Orlando bar popular with college students.

The charge was later re­duced to a misdemeanor count of resisting an officer without violence, and Zim­merman served eight months community service.

But now he’s in even more trouble. On the night of Trayvon’s shooting, Zim­merman claimed he was on his way to the grocery store when he spotted the youth, who was wearing a “hoodie” sweatshirt. He called police, and despite being told to re­main in his vehicle, he got out.

Zimmerman told authori­ties they exchanged words and the youngster knocked him to the ground with a punch in the nose. He claims that unarmed Trayvon be­gan slamming his head into the sidewalk before he ended the boy’s life with a single shot to the chest.

But nearby resident Mary Cutcher told The ENQUIRER she believes she heard Trayvon crying for help before a single gunshot rang out. Zimmerman claims he was the one shouting for help. But Mary, 31, insisted: “It sounded like a child or young man who was in distress.”

Cutcher’s roommate, Selma Mora Lamilla, 36, told The ENQUIRER she was the first to reach the crime scene near her home.

“I could see Zimmerman sitting on top of Trayvon, who was face down on the ground,” she recalled. “He was sitting on the kid’s back, straddling him, holding him face down in the dirt.

“Zimmerman was not do­ing CPR and didn’t appear to be doing anything else to help him.”

And now, in a shocking new development, both NBC and MSNBC are under fire for airing an "edited version" of the 911 call that plays up Zimmerman's alleged racist bias.