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A struggle ensued before a veteran Illinois police officer was found shot dead a month ago, authorities said Thursday.

Fox Lake officer Charles Joseph Gliniewicz was shot twice with his own gun, Lake County Major Crimes Task Force Commander George Filenko confirmed Thursday — once on the right side of his vest, and once in the upper left chest region.

The first shot hit the officer with the force of a "sledgehammer hitting you in the side," Filenko said. The second shot is believed to be the one that killed him.

There have been few leads in the mysterious death of Gliniewicz, who radioed dispatch on Sept. 1 that he was pursuing three suspicious men in a marshy area near an old cement plant before he was found dead.

Filenko told reporters that no theories have been eliminated in Gliniewicz's death. Nine samples of DNA were recovered at the scene, he added, and one has been confirmed to be a male. Swabs are being analyzed at crime labs to try to identify the others, although it's not clear whether the nine samples were from the day Gliniewicz was shot or from some time before.

Filenko gave few other details, but said according to the investigation's findings, "there were indications that there was a struggle that took place at the crime scene."

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Investigators continue to treat the case as a homicide, and Gliniewicz's death sparked a manhunt for the three suspects about whom Gliniewicz radioed. But questions have been raised about whether the officer could have committed suicide.

Gliniewicz's family has played down rumors that he took his own life.

His widow, Mel Gliniewicz, told "Crime Watch Daily," a Chicago TV show, this week that the accusations of suicide are "disrespectful, hurtful, irresponsible."

And his son, Gliniewicz's son, Donald "D.J." Gliniewicz, has said that the lieutenant "never once had a single suicidal thought."

Last week, task force spokesman Chris Covelli said that gunshot residue and ballistics tests "do not support or exclude any theory" about his final moments.

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When asked Thursday whether investigators were considering suicide as a possibility, Filenko replied, "Nothing is off the table."

But the case, he said, "is still an ongoing homicide investigation."

Lake County Sheriff spokesman Detective Christopher Covelli called it "an extraordinarily complex investigation with many different components."

"We're working very hard to keep the community informed," he said. "We understand the frustration."