Authorities said Wednesday they have positively identified the remains of a man that were unearthed in 2003 on private property southwest of Cambridge in Isanti County.

Donald Rindahl, 22, who was last known to live in New Brighton, was buried 3 feet underground on that land in Bradford Township sometime in late 1970 to early 1971, the Isanti County Sheriff's Office announced, thanks to meticulous DNA analysis.

Still left to be solved: What led to Rindahl's death and who, if anyone, is responsible.

"Based off … information from the family, as well as the scene in 2003, it is believed that Donald was a victim of homicide, but his death has been classified as undetermined," a statement from the Sheriff's Office read.

"It is further believed," the statement continued, "that there may still be people alive today who know what happened to Donald in 1970."

Capt. John Elder, chief spokesman for the Sheriff's Office, said the family suspects foul play because "they don't believe he would just take off and not ever communicate with them."

Rindahl's family members are asking for respect for their privacy, and they are declining interviews with the news media, the Sheriff's Office said.

The skeletal remains were discovered in August 2003 near Hwy. 47 and County Road 5 in two places by a man digging up a driveway with a Bobcat. The skull was located apart from the other remains.

At that time, the Midwest Medical Examiner's Office collected the remains and concluded they belonged to a white man in his 20s who had been buried there for anywhere from three to 28 years.

The Sheriff's Office on Wednesday spelled out the chain of forensic events that led to Rindahl's remains being identified.

The Minnesota Bureau of Criminal Apprehension (BCA) obtained from the remains a DNA profile that was entered into missing-person databases. A facial reconstruction also was done and publicized in 2004.

Investigators submitted DNA samples from families looking for a loved one, but there were no hits.

Then in 2019, Lisa Lovering, now chief deputy in the Sheriff's Office, turned to more current and enhanced DNA technology. The DNA that the BCA obtained was submitted to a lab in 2019 and again in 2020, but it was not producing a viable sample that could be analyzed by investigative genetic genealogy consultant Barbara Rae-Venter.

Last year, Rae-Venter referred the Sheriff's Office to Othram, a lab in Texas that uses a newer technology to build DNA profiles from skeletal remains. This is the same lab that recently identified the remains of missing Stillwater teen Sherri Ann Jarvis, who was found in Texas 41 years ago.

In October, Othram extracted a viable DNA sample and built a comprehensive DNA profile that was sent to Rae-Venter and the Isanti County Sheriff's Office. Within 24 hours, she had a match of a distant relative. From there, she built a family tree.

In November, the Sheriff's Office received a name of someone who Rae-Venter believed was associated with the remains.

From there, Lovering located two siblings of Rindahl. One of them confirmed that their brother had been missing since 1970. Family members were told that the FBI had been looking for him before his disappearance in connection with illicit drugs.

The Sheriff's Office obtained DNA samples from the siblings. The samples were submitted to the BCA to compare with the DNA originally extracted in 2003 from the remains.

In December, the BCA said the DNA comparison confirmed the remains as belonging to Rindahl.

Lovering said that when she reached the family by phone "there was disbelief" on the other end of the line.

"It was a random phone call that someone calling about their brother they hadn't seen in 51 years," she said during a news briefing Wednesday morning that KARE11-TV posted online. "I think once I got the DNA match, it set in a little more, but there's still a lot of unanswered questions for them. We don't know what happened. We don't know where he was, and we don't know who was involved."

In the effort to determine the cause and manner of Rindahl's death, law enforcement is asking anyone with information about this case to contact the Isanti County Sheriff's Office at 763-689-2141 or CrimeStoppers of Minnesota at 1-800-222-8477.