In a potentially stunning twist, authorities are investigating the possibility the Illinois police officer thought to have been gunned down in the line of duty instead might have killed himself in a staged suicide.

As Fox News first reported last week, two sources close to the case say evidence suggests the 30-year police veteran, Lieutenant Charles Joseph Gliniewiecz, 52, could have shot himself -- in what was originally described by police as an execution-style murder.

Now, as police continue to actively investigate the case as a homicide, they say they aren't ruling out suicide.  

Sources tell Fox News two shell casings were found about 100 feet apart from each other near Gliniewicz’s body, which was discovered face down. His hand was in a gun position, the firearm “dropped at his body.”  

One bullet hit Gliniewicz in his bulletproof vest. The second and fatal shot struck him underneath his vest, fired in a downward trajectory, near the heart.  There was no sign of a struggle or defensive wounds—especially one to save his own life.

The Lake County Coroner, Dr. Thomas Rudd, told Fox News that Gliniewicz died from a “single, devastating” shot to the torso. He said he hasn’t made a ruling in the death and that suicide is a possibility.

Immediately after Gliniewicz was discovered, a massive manhunt ensued including hundreds of local, state and federal officers. The team extensively searched the area by foot and with helicopter and dog teams but found nothing.

Two weeks after the officer’s death there are more questions than answers as police remain tight-lipped. There have been no arrests. There are no witnesses, suspects or concrete leads in the death of the father of four, who was regarded as a pillar of the community and known as “G.I. Joe.”

The drama began on the morning of Tuesday, September 1 when Gliniewicz radioed in from a remote, marshy area near Fox Lake, Ill., that he was beginning a foot pursuit with three suspects, two white males and one black male. Shortly after that, his radio communication cut off—leaving police with minimal description of the men.  

Minutes later, backup officers arrived and discovered Gliniewicz had been shot and killed. An enormous manhunt followed. Police quickly alerted the public to be on the lookout for the three suspects.

The FBI, ATF and Homeland Security participated in the investigation along with the Fox Lake Police Department, under the direction of Lake County Major Crimes Task Force Commander George Filenko.

The story gained national attention as teams of media crews flooded the quiet town.

In the following days, Filenko hosted a series of news conferences in which he told reporters and the anxious community that nearby traffic cameras and home surveillance systems captured video depicting what appeared to be the three suspects—but it would take time to verify what was on the tapes.

As the unsolved death investigation carried on into the Labor Day weekend, neighbors and tourists in the picturesque “Chain O' Lakes” area took to the streets and blue waters with caution. Three “cop killers” were on the run, but people weren’t quite sure who or what they should be looking for.

The tree-lined streets of the quaint community were lined with blue ribbons and signs in Gliniewicz’s honor. A long line formed at a print shop that was giving out free posters depicting Gliniewicz. A local Motorola company offered a $50,000 reward for a tip and information leading to an arrest.

The following Monday, Gliniewicz was given a ceremonial funeral attended by over 5,000 police officers from around the country. Thousands of mourners stood along the streets and in their yards as the procession of over 1,600 police cars took hours to drive the 18-mile route to the cemetery. Gliniewicz was hailed as a hero, the latest officer to be killed in the line of duty.

The next day, one week after Gliniewicz died, Filenko hosted his final news conference to date in which he told the public the three suspects who were caught on tape, as described in Gliniewicz’s radio call, were cleared. Receipts and affidavits showed they were not the cop killers.

Filenko said investigators still consider the officer’s death a homicide and were analyzing crucial DNA found at the crime scene—which they said does not belong to Gliniewicz. But he would not specify what it was.

As the mystery deepens and theories abound, police insist the investigation will be a “marathon not a sprint.”

Matt Finn is a Fox News correspondent based in the Chicago bureau.