Final moments of man found dead in tanning bed after 3 days revealed

More details have been revealed about the case of a man who was found dead in a gym’s tanning bed three days later.

In an interview with PEOPLE Magazine, the mother of the man identified as Derek Sink talked about his final moments before he was discovered lifeless.

According to Karen Wetzel, Sink signed up for a membership at Planet Fitness in Indianapolis on Nov. 8 as his girlfriend Heather and her daughter waited for him at a nearby store. He, however, did not contact them again so they ended up looking for him at the gym, but to no avail. They went home and reported him missing on Nov. 10, just one day before his dead body was found by a probation officer.

Wetzel said that Sink was dealing with drug addiction, adding that she believes his toxicology report will show there was fentanyl in his system.

Still, she described Sink as "a human being with value and worth" and as "the kindest person with the softest heart."

A spokesperson for the Indianapolis Metro Police Department told PEOPLE that an investigation is ongoing and the cause of his death is yet to be determined.

Tanning has been made unavailable at the Planet Fitness location since the incident happened.

McCall Gosselin, who serves as chief corporate affairs officer for the gym, said in a statement sent to PEOPLE that they're "deeply saddened" about what happened. "The franchise owner is working with the local authorities in their investigation," she added.

Gosselin also assured that the gym has "robust operational brand protocols in place," putting the safety and well-being of their members at the top of their priorities. "We are working closely with our local franchisee to ensure they are upholding those brand protocols,” she continued.