(CBS) – He was charged with a horrific crime: dousing his girlfriend and their apartment with gasoline and then lighting her on fire.

Gregorio Carmona was found guilty. But in a rare move, Judge Carol Howard reversed her decision and acquitted Carmona of murder and arson charges.

Carmona walked out of Cook County Jail a free man on Monday night after spending 4 ½ years behind bars.

Prosecutors said Carmona doused his girlfriend, Claudia Martinez-Rayo, with gasoline. He allegedly doused their Albany Park garden apartment with fuel, too, and then started a fire in 2013.

Carmona says he didn’t start the fire and heard a “big sound, like a boom.” Then he says he smelled smoke.

“I grabbed my daughter and I carry her out,” he tells CBS 2’s Suzanne Le Mignot.

Carmona says he went back to get his girlfriend, who had gone to bed.

“I tried to save her,” he says. “There was no way to get into the house.”

After Carmona was found guilty during a bench trial, his lawyer filed a motion for reconsideration, leading to the charges being dropped.

“What the state had here, at best, was a very weak, circumstantial case,” Carmona defense attorney Anthony Peraica says.

Lab tests showed no gas was on Carmona’s hands. A back door leading to a shared laundry room and Carmona’s garden apartment was always left open; and two weeks after the fire, a gang tagged the property with graffiti, including the word, “homicide.”

“We argued to the judge that this was Latin gangs taking credit for this fire and for the homicide that occurred at that location,” Peraica says.

He says a federal lawsuit can now move forward, naming Chicago police as plaintiffs after his client was wrongfully charged.

“They tried to do their best to put me in jail, forever,” Carmona says.

Chicago Police say they cannot comment on pending litigation.

The Cook County State’s Attorney’s Office issued a statement saying: “We are disturbed by the court’s decision. We are attempting to understand the basis for the ruling.”

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