Human remains recovered from a submerged 1960s Buick in the Mississippi River last month have now been confirmed as belonging to a Minnesota man who vanished nearly 58 years ago.

Earlier this week, the Benton County (Minnesota) Sheriff’s Office announced that the remains were positively identified as Roy Benn of Sauk Rapids, who was and was last seen on September 25, 1967, at a café in Sartell. At the time he disappeared he was 59.

The sheriff’s office said that they remained on the case over the decades even as previous investigations into his whereabouts were unsuccessful.

The big break came on Aug. 10, when boaters on the Mississippi River noticed a shape on their electronics that they suspected was a submerged vehicle. Authorities later responded to the spot and confirmed the discovery.

Fisherman Brody Loch, who located the car, attributed the discovery to “100% luck,” telling CBS affiliate WCCO, “If my buddy wouldn’t have caught that walleye, then we would have just kept on floating down and never would have found it.”

Three days later, the Stearns-Benton County Sheriff’s Office Dive Team recovered the 1963 Buick Electra.

“Investigators confirmed that the recovered vehicle was registered to Roy Benn,” the sheriff’s office said, adding that several items belonging to him were also found alongside the human remains, which were sent to the medical examiner’s office for identification.

The sheriff’s office further stated that on Thursday, Sept. 4, medical examiners at the Midwest Medical Examiner’s Office positively identified the remains as those of Benn through DNA analysis.

“The Midwest Medical Examiner’s Office continues to work on a determination of the cause and manner of Mr. Benn’s death,” the sheriff’s office said.

His cause and manner of death have yet to be determined.

The Minnesota Bureau of Criminal Apprehension said that Benn was last seen leaving the King’s Supper Club in Sartell carrying a large sum of money and wearing a dark suit, a French-cuffed white shirt and gold-and-pearl cufflinks.

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Benn owned an apartment building and an appliance service business in nearby St. Cloud, was considered financially comfortable and known to have substantial sums of cash. Authorities at the time said he may have been carrying thousands of dollars when he vanished, according to KNSI.

Benn was declared legally dead eight years after his disappearance, the outlet reported, noting that his loved ones maintain that he was happy with his life and would not have abandoned his family.

Police and the medical examiner’s office did not immediately respond to PEOPLE’s request for additional information.