One year after Robert Roos' mysterious death, the two people who deserve most to know what happened say they know the least.

Russ and Bertha Roos' grief has been accompanied by frustration, confusion and sometimes fear since their 33-year-old son, Robert, died from a massive head injury a day after he was found in the driveway of the rural Corcoran home where he lived with his parents.

Authorities have spent a year investigating the case yet have divulged little to Roos' parents, who are demanding to know what happened to their only son, a shy young man who studied at Stanford University.

"I want somebody to tell me, was this an accident? Was this a crime? Or what has happened here?" Russ Roos said in a recent interview at the family's home. "The information we get is this: 'It's under investigation and we can't discuss it.' Every which way we turn, we come to a roadblock."

The Hennepin County Sheriff's Office has declined to discuss its investigation into Roos' death with the Star Tribune, as did Hennepin County Medical Examiner Dr. Andrew Baker. Roos' death certificate says he died from complications of a blunt force head injury, but the manner of death -- homicide, suicide or accidental -- "could not be determined." Both Baker and a Sheriff's Office spokeswoman refused to say whether any of the three possibilities have been ruled out. Sheriff's Lt. Todd Turpitt and spokeswoman Lisa Kiava declined to discuss the case or say whether they're searching for a suspect.

"It's an open and active investigation," Kiava said.

Parents: Someone knows

Meanwhile, Russ and Bertha Roos say they've been left in the dark as telephone calls from investigators slowed, then virtually stopped.

"It's going into a cold case," said Bertha Roos, who is convinced someone assaulted her son but has no evidence of that. "Someone out there knows something that happened. They can't keep it quiet forever."

Nothing appeared to have been stolen from the home, and fingerprints, blood and DNA samples from the house belonged only to Roos and his parents. Investigators spent time on the roof of the family home and took aerial photos. Roos' parents say their son took dextroamphetamine for attention deficit disorder, which sometimes caused volatile changes in his mood. They say he never acted depressed or suicidal, but acknowledge the possibility that an accident or suicide could have been involved simply because authorities haven't ruled them out. They asked investigators to do so again this week, and received no answer.

Russ Roos said he's beginning to draw his own conclusion that investigators aren't looking for a suspect.

"If it's not a homicide, then why is it still an open case?" he said.

Unexplained injury

From a young age, Bertha and Russ Roos' adopted son was a computer prodigy, brilliant but at times socially awkward. He studied computer science at Stanford, but returned home after leaving the school a few credits shy of his graduation. For the next decade he lived in an upstairs bedroom of his childhood home, working on occasion as a live-in personal care attendant and trying to invent a new online social network. He was shy in social situations, his mother said, but got along well with his parents, who were happy to have him at home.

On the morning of Nov. 5, Roos was in bed when his mother left at about 7:30 a.m. for church and errands. His father was deer hunting in northern Minnesota. Bertha said she arrived home at noon to a sea of squad cars in the driveway. They questioned her and sent her to North Memorial Medical Center, where Russ joined her that afternoon. They were finally allowed to see Robert, who was on a respirator. Cuts and scrapes covered his toes, while another was on his shoulder, but they were likely not defensive wounds, the Rooses would be told later. They discovered afterward that his hands were also scraped. Hours later, Robert died. His heart and other organs were donated.

The family held a small funeral in Rogers and buried Robert in Iowa, but did not run an obituary in hopes of protecting the integrity of the investigation. In the ensuing months, the Rooses said they received calls from investigators about once a week. Those calls dwindled and they struggled to get any information -- including who discovered their son in the driveway and called 911.

Several searches, few answers

Multiple searches of the home revealed that Roos may have dabbled with marijuana or synthetic drugs. The Rooses say they were told that other than his prescription medication, no other drugs were found in his system. A detective provided them with a pamphlet on "bath salts" -- a man-made drug formerly available in head shops. The substance has since been outlawed in Minnesota and has been known to cause erratic and dangerous behavior in users.

"He said, 'I'd like to have you read this,' and I said I would never buy that theory," Russ Roos said.

Bertha Roos said investigators may have been led to the conclusion because she found a receipt for bath salts before her son died, and turned it over afterward. Police never found the synthetic drug, she said.

They also took his computers, and returned them to the family without saying whether they found anything. The Rooses are not sure whether all of it was returned.

They have been unable to access the autopsy report. Under the law, autopsy results are not available to family members in cases of homicide or undetermined deaths that are under active investigation, Baker said. However a representative from his office, along with Corcoran police and the Sheriff's Office, went over autopsy findings with the Roos family and tried to answer all their questions.

Bertha and Russ Roos fear their son's case will slip into obscurity. If investigators believe in one theory over another, they want to know.

"You cannot leave this undetermined forever," Russ Roos said. "It is not gonna fly."

Abby Simons • 612-673-4921