Later Sunday, Downing said the children had started talking to their grandparents about things they remembered from the night their mother vanished.

"They were beginning to verbalize more," said Downing. "The oldest boy talked about that they went camping and that Mommy was in the trunk. Mom and Dad got out of the car and Mom disappeared."

Susan Powell was reported missing Dec. 7, 2009. Josh Powell — who has denied any involvement in her disappearance — told police he last saw his wife around midnight, when he put their sons in the family’s minivan and took them on a late-night camping trip during freezing temperatures in Utah’s west desert.

Kirk Graves, Josh Powell’s brother-in-law and the husband of Jennifer Graves — both of whom had been estranged from Josh and believe he killed Susan Powell — said he views the fire as proof that Josh Powell killed his wife.

"In my personal opinion, this is Josh’s admission that he did it," Graves said. "I know others won’t interpret it that way, but I know that is what this was."

Graves said he and his wife had been pleased the boys would be able to stay with Coxes.

"Josh didn’t feel the same way, I guess," Graves said.

Graves said they got confirmation of the fire from Chuck Cox, who went to Josh Powell’s home and observed it burning.

"We’re still in shock," Graves said. "We’re almost shaky."

They visited their nephews over Thanksgiving in Washington, and had spoken to them on the phone since.

Graves said of Josh Powell’s mother, Terrica Powell, "She’s not doing well."

Graves said he plans to go Washington and be there for the Coxes and help with funeral arrangements.