FARGO — Aaron Thompson of Fargo was looking for answers a week after he found out his 5-year-old daughter Raven died in foster care on the Spirit Lake Indian Reservation in northeast North Dakota.

"They know who it is," he said during a vigil attended by about 25 people in front of the federal courthouse in downtown Fargo Wednesday night, May 13.

"Why isn't anything being done?" asked the 33-year-old father of four. "It sickens and saddens me that these people are out running about. I'm worried for other kids."

Amanda Vivier feels the same way. The leader of a city task force addressing the issue of missing and murdered indigenous people and a Native American spiritual adviser said she helped organize the vigil to try to help Thompson.

Even though he didn't have custody of the children, she said, he was still a parent.

After they learned a forensic investigation into the case hadn't even been started as of Wednesday, Vivier said, she became even more concerned.

"A lot of these cases on the reservations become cold cases, and the FBI doesn't do a thorough investigation," she said.

Amid the uncertainty and sadness, Thompson learned that his 7-year-old son, Zane, who was also in the same foster home, was "doing well" in the intensive care unit at Sanford Children's Hospital.

He still had not been allowed to see his boy, but was hoping to on Thursday.

Meanwhile, U.S. Attorney for North Dakota Drew Wrigley said late Wednesday afternoon that there were no updates on the death investigation.

"It's a top-level priority," he said. "I don't drag my feet in a situation like this."

He said the FBI, Bureau of Indian Affairs and two attorneys form his office are working on the case, conducting interviews and gathering time-sensitive information. No charges were filed as of Wednesday night.

Because of concerns from others on the reservation, Wrigley said they have been assured by the tribal social services agency that other children about whom tribal members were worried have been removed from the situation.

Generally, Wrigley said, his office is unable to confirm or deny the existence of an investigation, but he said this case is a clear exception where information needs to be released to reassure the public that an investigation is being conducted.

FBI spokesperson Kevin Smith verified earlier this week that the case is classified as a death investigation.

Tribal Chairperson Peggy Cavanaugh said Wednesday she couldn't comment on the investigation, although she wanted to express the tribe's sympathies to the families involved.

Vivier added there was "something wrong with the system" because of the delay in answers. She said she had been making numerous calls on the state and national level and to the FBI in the case.

Thompson believes there are serious problems on the reservation.

"There's too much wrongdoing going on there. We need some help up there," he said.

Thompson has been in trouble with the law, and that's why he doesn't have custody of his children. He spent 22 months in jail recently, but was hoping to earn custody back next month when he completed parole.

As for now, Vivier said Thompson deserves more answers, and that would help him receive at least some closure on the death of his daughter.

Thompson has two other daughters, ages 8 and 14, who are living with family members.