How Caleb Harris Died Can't Be Determined and He Had Decomposed to a Skeleton in Sewer System: Autopsy

His family has previously shared their grief while remembering him as a "happy go-lucky person" who "always had a smile on his face"

Authorities have released Caleb Harris' autopsy report but say that his cause of death "cannot be determined with certainty," citing, in part, the fact that he had decomposed to a skeleton by the time he was found in the Corpus Christi, Texas, sewer system.

On Tuesday, Aug. 6 — five months after the Texas A&M University student, 21, went missing and over a month after his remains were found in a wastewater well near his apartment — the Nueces County Medical Examiner’s Office released its findings about his manner of death.

In the autopsy report, which was obtained by PEOPLE, authorities said that at the time his remains were found, they were already in an "advanced state of decomposition and skeletonization."

“While no significant traumatic injuries are identified, the condition of the remains could have obscured subtle injuries and/or additional significant natural disease,” the medical examiners wrote, noting that his toxicology analysis came back negative.

“The exact details leading up to the terminal event and death are currently unclear,” the autopsy states. “Hence, the cause and manner of death are classified as undetermined at this time. If additional information becomes available in the future, the cause of and manner of death can be amended, if needed.”

Related: Caleb Harris' Family Speaks Out as Police Say Human Remains Found in Well 'Most Likely' Belong to the Student

Harris was last seen on March 4 near the school's campus in Corpus Christi, by his apartment complex on Ennis Joslin Road. Days later, his family told  Fox News that he went outside to pick up an Uber Eats order before 3 a.m. local time when he vanished.

The family added that Harris went for a walk with a dog he shared with his roommate, dropped the dog off and disappeared after he left to pick up his order. (Uber previously confirmed to PEOPLE that Harris' order was completed and that the delivery person continued to make deliveries that morning.)

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On Tuesday, June 25, the Corpus Christi Police Department announced that a Corpus Christi city employee discovered human remains the day before in a 40-foot-deep well, before notifying police around 3:30 p.m. local time.

The local Corpus Christi Fire Department then “donned hazardous material suits to retrieve the remains from within the well."

On July 17, the CCPD revealed on Facebook that analysts with the University of North Texas Center for Human Identification determined the remains "most likely" belonged to the missing student, after comparing DNA samples from the remains with DNA samples taken from his parents.

As previously noted, the remains "bore no obvious signs of homicide," per the CCPD.

Although there may always be unanswered questions about Harris' death, police previously shed some light on how he may have ended up in the sewer system to begin with.

Deputy Chief Billy Breedlove of the Corpus Christi Police Department previously told PEOPLE that while it's possible that Harris was "harmed and then was put there" — although authorities have no evidence of foul play — it's also possible that an accidental fall was to blame.

In an interview conducted on Thursday, July 18, Breedlove said that around 3:03 a.m. on March 4, Harris sent a Snapchat photo to a friend that showed a small bridge located a few hundred feet away from his apartment complex.

About 600 feet from there, investigators found a manhole, Breedlove said, noting that its cover "had been knocked aside."

Although he couldn't say for certain how Harris entered the manhole, Breedlove said police do believe that the open manhole was Harris' point of access into the sewer system.

Related: Caleb Harris’ College Will 'Honor His Legacy' With Memorial Ceremony in the Fall: 'Let Us Remember'

In a eulogy at his memorial service in July, uncle Jeff Wright remembered Harris as a "happy go-lucky person."

“He always had a smile on his face. He was very close to his family, talking to his mom and dad daily," Wright continued, noting that Harris "had many passions throughout his life: guitar, music, cooking, cars, biking, fishing, hunting, camping, skateboard, Legos and anything water-related."

"With these passions, he wanted his friends and family to experience the joy he got from them," Wright added, noting that Harris spent his final Saturday before he went missing showing his mom all his favorite spots in Corpus Christi.

Wright added, “Caleb’s character will live through his family until we see him again in heaven."

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