Lt. Charles Joseph Gliniewicz’s son said he doesn't believe his father committed suicide and he expressed confidence in the work of the Illinois investigators looking into his dad’s mysterious death.

Donald “D.J.” Gliniewicz told the Daily Herald that his family is upset at the suggestion his father could have been responsible for his own death.

“My father never once had a single suicidal thought in his life,” Gliniewicz said.

"My entire family isn’t happy"

- Donald Gliniewicz

The drama began on the morning of Sept. 1 when Gliniewicz radioed that he was in pursuit of three suspects – two white males and one black male. He requested backup, but when responding officers arrived, they found Gliniewicz dead.

Sources told Fox News two shell casings were found about 100 feet apart from each other near Gliniewicz’s body, which was discovered face down. The firearm was “dropped at his body.” One bullet had hit Gliniewicz in his bulletproof vest. The other, a fatal shot fired from a downward trajectory, struck him underneath the vest, near his heart. There was no sign of a struggle or defensive wounds.

Authorities are still waiting for the results of tests on DNA found at the scene that did not belong to Gliniewicz.

Lake County coroner Dr. Thomas Rudd told Fox News last week that he hadn’t made a ruling in the officer's death and that suicide was a possibility. Fox News also reported last week that two sources close to the case said evidence suggested Gliniewicz, 52, a 30-year veteran of the force, could have shot himself.

“For someone who didn’t know him to go out and question that, then also release information that could jeopardize the investigation…my entire family isn’t happy,” the younger Gliniewicz said.

Authorities are still waiting for the result of ballistics that could determine if Gliniewicz was shot with his own service weapon. Test results determining if the officer had gunpowder residue on his hand also have yet to be revealed.

Investigators have little evidence to guide them – a vague description of possible assailants being one of the best pieces – but D.J. Gliniewicz said he remains confident they’ll make progress.

“I know they are doing their hardest to get to the bottom of this,” Gliniewicz said. “I definitely do not want them to speed through the investigation and skip over important details.”

A massive manhunt for the three individuals Gliniewicz said he was chasing has so far proved fruitless.