The North Dakota Supreme Court denied an appeal by the parents of North Dakota State College of Science student Andrew Sadek, who was found dead after becoming an informant to drug investigators.

Justices in an opinion released Tuesday upheld Judge Jay Schmitz’s dismissal last year of the wrongful death lawsuit. The vote of the 5-person Supreme Court was 4-1.

The Sadeks sued the Richland County Sheriff’s Department, one of its deputies and the county, alleging their son was killed because he was coerced into becoming a drug informant.

The judge ruled there was no evidence that the sheriff’s deputy directly caused Sadek’s death or that the county acted negligently in assessing the dangers of being an informant.

The 20-year-old agreed to become an informant in exchange for lenience after he was caught selling marijuana. His body, with a gunshot wound to the head and rocks in his backpack, was found in the Red River in June 2014.

Although an autopsy attributed his death to the gunshot, it classified the death as “undetermined” and didn’t conclude whether he shot himself or whether someone else shot him.