(CNN) — An Atlanta-area police officer who was arrested for concealing the death of a 16-year-old girl has now been charged in her kidnapping and murder, police said Wednesday.

Miles Bryant, 22, was arrested on preliminary charges of falsely reporting a crime and concealing the death of another in connection with Susana Morales’ death after the girl’s remains were found earlier this month. She had been missing since July.

Investigators have found a firearm that Bryant had said was stolen, Gwinnett County Police Chief James D. McClure said at a briefing Wednesday.

Bryant reported a gun stolen on the same morning that Morales was reported missing in July. The weapon was found during a February 7 search of the scene where the teen’s body was discovered, said the chief.

Police traced the firearm back to Bryant, and “at that point he became a person of interest, so we began watching him,” McClure said.

At the time, Bryant was an officer for the Doraville Police Department in DeKalb County, which neighbors Gwinnett. He was fired after officials were made aware of the charges against him, according to a city official.

Bryant remains in custody in Gwinnett County Jail, according to online jail records. It is unclear if he has retained an attorney.

Police have not disclosed information about how Morales died. Morales was not shot, the chief said, without providing details on the state of the 16-year-old’s body.

McClure declined to provide information on a possible motive.

On July 26, Morales was visiting a friend at an apartment complex on Indian Trail Road, according to McClure. She was taken between 10 p.m. and 10:30 p.m. as she was walking back home, and investigators believe that she was killed sometime between 10:30 p.m. and 2 a.m., the chief said.

She was reported missing the next morning, July 27, at 9 a.m. Bryant reported the gun missing at 11 a.m., McClure said.

“We have a very solid case, and we’re confident,” said the chief.