The family of a North Dakota college student who was a confidential informant for a drug task force filed a wrongful death lawsuit Monday accusing a sheriff's department, a deputy and the county of failing to ensure the 20-year-old's safety.

The body of 20-year-old Andrew Sadek was found about two years ago in the Red River, which separates North Dakota from Minnesota, not far from where he attended college in Wahpeton. An autopsy concluded Sadek died of a gunshot wound to the head but the manner of death was "undetermined," according to the complaint brought by John and Tammy Sadek.

Their suit names as defendants Richland County Sheriff's deputy Jason Weber, who was part of the task force, as well as the county. It says the defendants failed to train Andrew Sadek to perform undercover operations and failed to "reasonably supervise" him.

A spokeswoman for the North Dakota attorney general's office, which is defending the lawsuit, was not immediately available for comment.

The Sadeks are asking for unspecified economic damages, including the cost of the memorial, and non-economic damages related to mental anguish, emotional distress, grief and loss of companionship.

A report by the North Dakota Bureau of Criminal Investigation said Sadek got in trouble with the law in April 2013, when he twice sold marijuana to a confidential informant. Both transactions were small -- $20 and $60 worth of drugs -- but they took place in a school zone, making the potential charges against him serious felonies. Later that year, drug task force agents searched Sadek's dorm room and said they found a grinder containing marijuana residue. The next day, Sadek completed paperwork to become a confidential informant, making three drug buys for the regional task force over the next three months.

The task force didn't hear from Sadek after that.

The family does not believe Sadek killed himself. A backpack full of rocks was tied around Sadek's body and he was wearing different clothes from the time he was last seen, the suit said.

Lawyers for the family sent a letter to federal authorities in April asking the U.S. Department of Justice and FBI to investigate the case. The Justice Department said it was reviewing the case. There was no response from the FBI, the family's lawyers said.