The young sons of Josh and Susan Powell began to "verbalize more" about their missing mother, suggesting that she was in the trunk of their father's car on the night she disappeared in 2009, an attorney for the woman's parents said.
Josh Powell had been named a "person of interest" in his wife's disappearance and had lost custody of the boys, who were just 7 and 5 when they and their father died in an explosive fire authorities believe he set at a home in Graham, Wash. Susan Powell had vanished while the family lived in West Valley City, Utah, and is believed dead.
The boys, Charles and his younger brother Braden, were beginning to talk to their maternal grandparents, Chuck and Judy Cox, about the night their mom disappeared, the Cox's attorney, Steve Downing, told the Associated Press.
"They were beginning to verbalize more," said Downing, whose clients had custody of the children. "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."
Josh Powell had long claimed he took the boys camping in freezing weather and returned home the next day to find his wife gone.
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 the 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.
The investigator did not return a subsequent message regarding the children's assertion that their mother had been in the trunk of the family's car on the night she disappeared.
Meanwhile, Pierce County Sheriff's Sgt. Ed Troyer says Josh Powell's father, Steve Powell, is on suicide watch at the jail where he faces charges of child porn and voyeurism.
An email Josh Powell sent to his attorney just minutes before he apparently set the fatal blaze was simple and short, a farewell to the world after two years of scrutiny by police, prosecutors and the media.
"I'm sorry, goodbye," Powell wrote in the email to Jeffrey Bassett, days after he was denied custody and ordered to undergo a psycho-sexual evaluation.
The Sunday blaze at Powell's home brought yet another tragic twist to the story that began with Susan Powell's disappearance more than two years ago. 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.
The social worker called her supervisors to report that she could smell gas. Moments later, the home burst into flames, igniting an explosion that neighbors said rattled their houses.
Troyer said it appeared an accelerant was used to make the house burn faster.
Susan Powell, a pretty 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 around Topaz Mountain, a popular spot for rock and gem hunters. That site is about 30 miles south of where Josh told police he went camping with the boys.
The search proved fruitless and Powell moved to Washington, where his father lives. Steven Powell, 61, was subsequently arrested there and accused of secretly videotaping young girls and women -- including Susan Powell -- taking baths and using the toilet in neighborhood homes.
The elder Powell has claimed in previous interviews that he and Susan Powell were falling in love and even implied a sexual relationship had occurred.
"Susan was very sexual with me," he said in one interview at the time. "We interacted in a lot of sexual ways because Susan enjoys doing that."
Chuck Cox denies his daughter had any interest in her father-in-law.
Custody of Charles and Braden was given to the Coxes 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.
In what would be the final custody hearing last Wednesday, Josh Powell pleaded in vain with a judge to return his children.
"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."
The Associated Press contributed to this report.