The mother of Jelani Day, a graduate student whose body was discovered in the Illinois River on Sept. 4, is still seeking answers for her son's mysterious death. Carmen Bolden Day made a virtual appearance on Good Morning America, where she opened up about the strange and devastating case. 

Day's body was identified on Sept. 23 by the LaSalle County Coroner through forensic dental identification and DNA testing. His personal belongings such as his car, wallet and lanyard with his school ID were found an hour away from his Bloomington home in Peru, Illinois.

"I'm very upset because I can't even look at my son's body. His body has deteriorated to the point where I can't say a proper goodbye to him," she said.

Authorities are currently looking into an unidentified man who was captured on camera knocking on the door of a home located not far from Day's remains. Police have since described the case and the evidence as "unusual." Day's mother is continuing her plea to the public for any information relating to his death. 

"Jelani did not disappear into thin air," Bolden Day shared. "Somebody knows something, somebody's seen something and I need somebody to say something."

An official cause of death hasn't been released as of yet.

An attorney representing the family, Hallie Bezner, explained to Good Morning America that there has to be more to this story — especially considering that Day had never visited Peru before his body was found. 

"The wallet was found in a different area. The lanyard, which … had a school ID on it, was not found with the wallet, it was found in a different area — the area with some clothes that were found last week," Bezner said.

Previously, Bolden Day called out Bloomington and Peru police for allegedly not doing enough in their investigation to find her son. She also expressed frustration after seeing the case of Gabby Petito, a young white woman, widely covered in the media.

Investigators are now trying to retrace the graduate student's last days, reports ABC7 Chicago. The mother said that the FBI's Behavioral Analysis Unit has joined the case. 

"I don't understand that, really, but whatever it takes to find out what happened to him, that's what I want them to do," Bolden Day said, per People. "I want them to use their tools and their resources so that we can find out what happened to Jelani, because he did not disappear into thin air."

Bolden Day described her son as "ambitious" and "driven." 

"He was focused," she continued. "He was energetic. He was full of life. Jelani was a person that you couldn't help but love."