(CNN) The funeral for 25-year-old Jelani Day, an Illinois graduate student whose body was identified nearly a month after he was reported missing, was held Tuesday in Danville, Illinois.
About 30 people attended the ceremony, including civil rights leader the Rev. Jesse Jackson and several members of his Rainbow Push Coalition, CNN's Omar Jimenez reported.
Day was reported missing in Bloomington, Illinois, on August 25 and his vehicle was located a day later about an hour north in Peru, Illinois.
An initial search on August 26 included K-9 units from Illinois State Police, aerial drone searches by local jurisdictions and ground searches, but nothing was found, said Officer John Fermon with the Bloomington Police Department.
Authorities returned on September 4 following a tip and found the body that would later be identified as Day's floating in the Illinois River. The LaSalle County Coroner said the cause of death is unknown, pending further investigation.
The family has also hired an independent private forensic pathologist to conduct a second autopsy, but no results from that have been released.
"I just saw one of the best things that God blessed me with go in the ground, and I will never get to talk to him or see him again ... I don't even have words to tell you what it's like," Day's mother, Carmen Bolden Day, said following the funeral.
"I don't know why I'm burying Jelani. I don't know what happened to Jelani, so I don't have any closure," Bolden Day said.
Day's family has been critical of authorities' efforts in the case. "To them, Jelani didn't mean anything," Bolden Day told CNN last month.
"There is no effort. There is no push. There is no nothing that was being done about my son."
"Me and my kids, me and everybody that never knew Jelani -- my family, friends, strangers -- did all the leg work," Bolden Day said. "My son didn't get any type of help ... He didn't deserve this."
Fermon defended the investigation and said, "We're lucky the story actually exploded as well as it did, which may or may not have led to the tips that came in." Fermon added that the search for Day involved 10 agencies and included specialized teams in the Peru area where the vehicle was found, with FBI assistance.
Jackson has also been critical of the authorities' response in Day's case. "We're not going to stop until it's over," he said.
Jackson has called for FBI and the US Department of Justice to "conduct a thorough investigation because it smells like another Emmett Till case all over again," he said in a statement, referring to the case of 14-year-old Till who was murdered in Money, Mississippi, in 1955.
Jackson said he is "committed to helping Mrs. Day," noting that Till's mother held an open casket funeral "so the world could see the horrible face of racism."
Day's mother said nothing in her son's life "would make you think he deserved to be found face down in a river."
Day was studying to be a speech pathologist, according to his mother, who said he was "outgoing, smart. He loves to have fun. He's energetic. He is sweet and compassionate. He's kind and caring," Jackson's statement said.