The Powell boys have been making the statement to their grandparents, Chuck and Judy Cox, for years, the attorney said, adding the boys mentioned their mother may have been looking for crystals in the mine.
Another lawyer representing the Cox family 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 attorney Steve 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."
The attorney said Charlie Powell drew a disturbing picture as a part of a school assignment several months ago. The drawing depicted the boy's father driving the van with Charlie and Braden sitting in the backseat, and their mother in the trunk.
"There was a subsequent question with regard to, 'Why is your mother in the trunk?' And his response was simply that he didn't know, but his mother and father had gotten out of the van, and his mother then got lost," said Downing.
Downing also said investigators with the West Valley City Police Department in Utah led the Cox family to believe Josh Powell would be arrested for the murder of his wife sometime this summer. No additional details were given.
The news came a day after Josh Powell and his two boys were killed in a massive explosion at their home in Graham. Powell had left a simple and short farewell to the world after two years of being scrutinized in the media, hammered by police and questioned by judges, prosecutors and social workers, living his life under a microscope since the day his wife vanished.
"I'm sorry, goodbye," Powell wrote in an email to his attorney just minutes before authorities say he set fire to his home, killing himself and his two young sons days after he was denied custody and ordered to undergo a psycho-sexual evaluation.
Det. Ed Troyer on Monday said Powell sent longer emails to his pastor and family members, mostly instructing them on how to handle his affairs after his death. One of the emails stated, "'I'm sorry. I can't live without my boys,"' said Troyer.
Those emails were also sent just minutes before the deadly blast, Troyer said, and there was no way the recipients could have prevented the tragedy.
"He had taken boxes of toys and books and donated them to the goodwill sometime over the weekend," Troyer said. "So this was definitely a deliberate, planned-out event."
Troyer added two 5-gallon cans of gasoline were found inside the home near the bodies, and a preliminary examination showed the victims had no gunshot wounds on their bodies.
"There is no indication about Susan (Cox Powell) in anything that we have found so far," said Troyer.
Chuck Cox said he was at church on Sunday when he learned of the fatal explosion.
"I went, 'What?!'" he said, adding he and the bishop immediately drove to Powell's home.
"That house burned completely. He wanted the whole place to go," he said. "They're gone, and I said, 'OK, what do I do now?"'
Cox said he always suspected his son-in-law was capable of taking drastic measures.
"I knew that it was possible. I knew that he was capable of something if he was pressured and pushed," he said. "If he felt there was no hope, he was capable of ending their lives and his life. But to do it in such a manner - by burning your own children - I just couldn't believe that would've happened."
The Sunday blaze at Powell's home brought yet another twist in the very public scandal that began when Susan Powell vanished in 2009. The case had since spiraled into a salacious saga of finger-pointing and accusations of sex and lies - and now the unthinkable loss of two young lives caught in the crossfire.
A social worker brought the two boys to Josh Powell's home Sunday for what was to be a supervised visit. They rushed toward the home, leaving the social worker behind. By the time she got to the door, Powell had let his sons in but locked her out, Graham Fire and Rescue Chief Gary Franz told The Associated Press.
Investigators tried to fill in holes Monday in the case with an arson investigation at the home and autopsies on Josh Powell and his sons, said Troyer. Local detectives also are meeting with police from West Valley City, Utah, who have been looking for Susan Powell.
Steve Richards, assistant chief of Graham Fire and Rescue, said crews were assessing the remnants of the home to determine how the fire began. He said responders arrived on scene about three minutes after getting the call and found flames already through the roof.
"It was just devastation," he said.
Fire investigators were slowly moving around the home Monday morning, measuring areas both inside and out. All the bodies were found Sunday in one room in the middle of the home, Troyer said.
A candle light vigil was held Sunday night for the boys outside the 7-year-old's school in Puyallup.
"Who could kill their kids and do this? He's the only one who can answer that and he's gone," Troyer said of Josh Powell.
Chaplains have been working with the family of Susan Powell.
Josh Powell's father also was informed of the death in the jail in Tacoma where he's being held for investigation of voyeurism. He's on suicide watch, Troyer said.
The Washington Department of Social and Health Services said the social worker who brought the boys to Josh Powell's home for what was to be a supervised visit is "suffering from grave emotional trauma as a result of the horrific event." The department will conduct a formal child fatality review.
She did all she could, Troyer said.
The social worker called her supervisors to report that she could smell gas. Moments later, the home burst into flames, igniting an inferno that neighbors said rattled their houses.
Susan Powell, a 28-year-old mother of two, was reported missing Dec. 7, 2009, after she failed to show up for her stockbroker job in Utah.
Authorities in the couple's hometown of West Valley City, about 10 miles outside Salt Lake City, quickly turned their attention to Josh Powell. He's been the only "person of interest" in the case, but had repeatedly denied any involvement in her disappearance.
"I would never even hurt her," a tearful, red-eyed Josh Powell told CBS' Early Show in August. "People who know me know that I could never hurt Susan."
About a month later, police spent 12 days in the remote central Utah desert looking for clues, and Josh Powell and his father, Steven, quickly disappeared from the limelight. The search area around Topaz Mountain, a popular spot for rock and gem hunters, was about 30 miles south of where Josh told police he went camping with his two children in the hours before his wife's disappearance - his steadfast alibi.
Police turned up no clues in their desert search, but a day before ending it, Steven Powell, 61, was arrested at his Washington state home and accused of secretly videotaping his daughter-in-law, other women, and young girls taking baths and sitting on the toilet in neighborhood homes.
The elder Powell is now jailed and facing child porn and voyeurism charges. He claimed in previous television interviews that he and Susan Powell were falling in love and even implied a sexual relationship had occurred.
"Susan was very sexual with me," Steven Powell said in one interview at the time. "We interacted in a lot of sexual ways because Susan enjoys doing that."
Susan's father denied the allegations and said Steven Powell had been initiating unwanted sexual advances, and that his daughter had no interest in her father-in-law.
Troyer on Monday called Steven Powell's claims "a complete lie."
"It was the other way around," he said.
The children, 5-year-old Braden and 7-year-old Charles, were ordered by a judge to then go live with Susan's parents as the parallel cases were investigated.
The custody matter got so heated that at one point a court commissioner in Washington state ordered Chuck Cox and Josh Powell to keep 500 feet apart.
Custody hearings continued, with the latest on Wednesday, during which Josh Powell pleaded with a judge to return his children to him.
"For over four months already, my interactions with my sons and many other aspects of my character have been investigated and documented by" social services, he wrote in an affidavit to the court. "I have proven myself as a fit and loving father who provides a stable home even in the face of great adversity. ... It is time for my sons to come home."
But the judge ruled against him, ordering the children to remain with Susan Powell's parents, at least until Josh Powell underwent a psycho-sexual evaluation, a process more often used as an assessment tool by courts to determine whether a defendant, largely in sex crimes cases, is likely to reoffend. In this case, the judge ordered it in light of the explicit material found on computers inside Steven Powell's home that led to his arrest.
Sherry Hill, a spokeswoman for the Washington state Department of Social and Health Services, said the social worker who was with the children Sunday was not a Child Protective Services employee but a contract worker with a private agency that supervises visits for the state.
"The visit supervisor for this particular agency had taken the children to the home. When she does that, she sits through the visit and might take notes on her observations," Hill said. "She pulled up in the car, and the kids ran out ahead of her. He closed the door and locked it. She wasn't able to get in, and that's when she smelled gas."
Bassett said he represented Powell free of charge because "every parent deserves the right to an attorney." Powell called or emailed him at least once a day, and often more than that, and in their conversations "he never once admitted doing anything regarding Susan. In fact, he denied it."
Sgt. Mike Powell of the West Valley City Police Department in Utah said it was too soon to say how Josh Powell's death may impact their probe.
"Quite frankly, this has obviously quickly unfolded up in Washington and we're obviously just working through the details ourselves here," said Powell, who is not related to the family.
West Valley City's police chief flew to Seattle Monday to help support the Cox family.
"It is really a difficult time," said Thayle "Buzz" Nielsen. "A whole family's basically gone and they're trying to adjust to that. We're up here to lend some support there and then check with police and see how they're doing and see if we can be of any assistance."
var so = new SWFObject("http://hosted.ap.org/interactives/2011/susan-powell/content.swf?SITE=KOMOTV", "ap-susan-powell", "640", "560", "10", "#FFFFFF"); so.addParam("base","http://hosted.ap.org/interactives/2011/susan-powell/"); so.addParam("allowFullScreen","true"); so.addParam("allowScriptAccess","always"); so.useExpressInstall("http://hosted.ap.org/specials/interactives/template_items/expressinstall.swf"); so.write("ap-susan-powell");