The police say the body of Timothy Cunningham, a rising star at the Centers for Disease Control and Prevention, was recovered from an Atlanta river on Tuesday, more than six weeks after he disappeared.

Cunningham, a CDC commander, went mysteriously missing on February 12.

The circumstances of Cunningham's death remain unclear, but the police said they don't suspect foul play in the case, and they believe he drowned somehow. He was wearing his favorite running shoes when his body was found, police said.

The mystery surrounding the February disappearance of a 35-year-old Centers for Disease Control and Prevention worker ended tragically this week, with the Atlanta Fire Rescue Department finding the CDC commander's body in a river late Tuesday evening.

The Atlanta Police Department confirmed to Business Insider that Timothy Cunningham's body was recovered in the Chattahoochee River in northwest Atlanta. Cunningham was wearing his favorite jogging shoes when he was found by a group of fishermen, police said.

Cunningham left work at the CDC feeling sick on February 12, then tried to call his mom on his drive home, but hadn't been heard from since. Timothy Cunningham. Atlanta Police Department

Maj. Michael O'Connor of the Atlanta Police Department said in February that Cunningham had recently been turned down for a promotion at work, and left feeling ill shortly after his supervisor explained why he'd been passed over.

Cunningham drove off that day and was never seen alive again, even as his car, credit and debit cards, dog, keys, and cellphone were all recovered at his home, the police said.

"We found that to be an unusual circumstance in a missing persons case," Major O'Connor told reporters at a press conference on Thursday afternoon. The only thing police said they found in Cunningham's pockets when his body was recovered were three crystals.

Police said they "knew he was a collector of crystals."

The muddy river spot where the officer was found wasn't too far from his house, but there weren't any roads or running trails nearby, so it's not clear exactly how Cunningham got in there. Police say they'd conducted a "very thorough" search of the riverbanks in that area on February 23, but didn't find any signs of the missing commander.

"We may never be able to tell you how he got into the river," O'Connor said. Doctors who've examined his body say there's no evidence of trauma or foul play, and they believe the cause of death is drowning.

Cunningham's father told The New York Times in February that he'd been worried about his son recently because he didn't seem like his usual self in conversation. His sister, Tiara Cunningham, the last family member who spoke with Cunningham before he disappeared, said she felt lost without her brother.

"I feel like I'm in a horrible 'Black Mirror' episode," she told The Times.

Friends also found the disappearance troublingly out of character.

"He has this pristine service record and background," Cunningham's friend David Calloway told NBC News.

Cunningham had an impressive career in public health, and the Atlanta Business Chronicle named him one of 2017's "40 under 40." He held a master's degree and a doctorate from Harvard's School of Public Health.

At the CDC, Cunningham was a team leader and researched health differences related to race, ethnicity, socioeconomic status, gender, and geography. The agency said he was an excellent officer and employee who had received an early promotion to commander last July.

On March 12, exactly one month after Cunningham went missing, the CDC's acting director, Anne Schuchat, released a statement saying the agency had not given up hope that he would be found alive.

"If Tim reads this message, we hope you come home soon," she wrote.

The agency said he'd been deployed to work on numerous public-health emergencies, including Superstorm Sandy, the Ebola outbreak, and the Zika outbreak.