Nwankwo went missing on October 30 after leaving a Schaumburg nightclub. A cab driver reportedly brought him home from a Halloween party. Detectives say the man's boot was found near his home's mailbox.
Nwankwo was reported missing by his mother November 1.
Investigators say there is no indication any foul play was involved.
Family members say Nwankwo had a mild form of autism.
"There's a lot of individuals that care for and were close to my brother. And so to all those people, it's heartwarming to see the amount of love and respect that he garnered from the community," said Victor Nwankwo, brother.
"It's hard to lose him because he was, especially now that the holidays are coming, he was the one that always remembered everyone's birthday and remembered everyone's special occasion," said Evelyn Nwankwo, sister.
Fire department teams used side-scan sonar to search the pond behind the home Nwankwo shares with his mother. Nwankwo's father died several years ago.
Police continue to investigate and are awaiting autopsy results.