ATLANTA -- The Fulton County Medical Examiner said a researcher at the Centers for Disease Control and Prevention (CDC) whose body was discovered in the Chattahoochee River last month died of suicide by drowning, CBS Atlanta affiliate WGCL-TV reports. Authorities said Timothy Cunningham's body was partially submerged in water and mud on the west bank of the river.

Cunningham, who worked as an epidemiologist in the CDC's chronic disease unit, had been missing since Feb. 12 in Georgia. He left work early that day saying he wasn't feeling well, and wasn't seen again.

Police said Cunningham had been disappointed about being passed over for a promotion in February. But the CDC disputed that, saying that Cunningham been promoted to commander effective July 1 "in recognition of his exemplary performance in the U.S. Public Health Service."

According to Cunningham's next-door neighbor, Viviana Tory, Cunningham said something odd to her husband the day he went missing.

Get Breaking News Delivered to Your Inbox

"He told my husband to tell his wife -- me -- to erase his cellphone number from my cellphone," Tory said.

Cunningham's parents reported him missing on Feb. 16 after they went to his home and found his belongings and vehicle there.

The autopsy report has not been concluded at this time.