(Graham, WA) - Days after a judge ruled against him in a child custody hearing, a father of two young boys apparently blew up a house Sunday with all three inside — a tragic ending to a bizarre, long-running case that began when the man's wife went mysteriously missing in Utah.

A social worker brought the two boys to Josh Powell's home for what was to be a supervised visit, and Powell let his sons inside — but then blocked the social worker from entering, Graham Fire and Rescue Chief Gary Franz told The Associated Press.

The social worker called her supervisors to report that she could smell gas, and moments later the home exploded.

Sgt. Ed Troyer, Pierce County sheriff's spokesman, said emails Powell sent authorities seemed to confirm the Powell planned the deadly blast. Troyer didn't elaborate on the contents of the emails.

Jeffrey Bassett, who represented Powell in the custody case, said he received a three-word email from his client just minutes before Powell and the two boys died. It said, "I'm sorry, goodbye."

The email arrived at 12:05 p.m. Sunday, about 10 minutes before the explosion, but he didn't see it until two hours later, when others told him Josh and the boys had been killed. He said he knew Josh was upset after being ordered to undergo a psycho-sexual evaluation recently, but he didn't see this coming.

Powell was under investigation in the disappearance of his 28-year-old wife Susan from their West Valley City home in December 2009. He claimed he had taken the boys on a midnight excursion in freezing temperatures when she vanished.

The children, 5 and 7, had been living with Susan Powell's parents since Josh Powell's father Steven was arrested on child porn and voyeurism charges last fall. On Wednesday, a judge had denied an attempt by Josh Powell to regain custody, saying she wouldn't consider returning the two boys to their father until he underwent a psycho-sexual evaluation.

Sherry Hill, a spokeswoman for the state Department of Social and Health Services, said the social worker who was with the children 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."

Lawyer Steve Downing, who represented Susan Powell's parents, Chuck and Judy Cox, in the custody fight, said: "It's the most horrifying thing you can imagine happening ...The Coxes are absolutely devastated. They were always very fearful of him doing something like this, and he did it."

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, which is handling the investigation into Susan Powell's disappearance, 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," Powell said Sunday.

"We are in contact with authorities," Powell added. "It's obviously an ongoing situation in Washington at this point."

Kirk Graves, 39, of West Jordan, Utah, Josh Powell's brother-in-law, said he and his wife, Jennifer, were stunned by the news. (Jennifer Powell Graves is Josh Powell's sister.)

"It's a shock. A total complete shock," he said. "We never contemplated the idea he would do something like this. You just don't expect it from a father."

Kirk Graves said he and his wife think Josh Powell deliberately set off the explosion to kill him and his sons.

"His world was falling apart around him and he was going to lose his boys and get arrested for Susan's disappearance," he said. "He's a narcissist and he has no love for anyone but himself.

Powell timeline

• Noon, Dec. 6, 2009 — Susan Powell, 28, and her two sons attended church services at the Hunter 36th Ward, and then walked home with friend Kiirsi Hellewell.

• Afternoon, Dec. 6 — Neighbor JoVonna Owings dropped by the Powell's home on Sunday afternoon to visit with Susan. The family had pancakes and eggs for dinner. Susan, who was feeling ill, lied down for a nap about 5 p.m. Owings left, as did Josh Powell, who said he was taking his two sons sledding.

• 8:30 p.m., Dec. 6 — A neighbor saw Josh Powell as he returned home and pulled into his garage.

• 12 a.m. to 12:30 a.m, Dec. 7 — Josh Powell said he left home with his two sons, then ages 2 and 4, to go camping at the Simpson Springs Campground, about 25 miles west of Vernon in the remote west desert of Tooele County while Susan went to sleep.

• 9 a.m. to 10 a.m., Dec. 7 — The Powell's daycare provider became alarmed when the couple failed to drop off their sons on schedule and she could not reach either parent by cell phone or at their home. She contacted Josh Powell's mother and sister, who called police after they could not locate the pair. Police broke into the Powell's home and find no one but notice two fans blowing on a wet spot on carpet in the home.

• Evening, Dec. 7 — Josh Powell and his two young sons returned home between 5 p.m. and 6 p.m. He was taken to the West Valley Police station to be questioned.

• 11 a.m., Dec. 8 — Susan's father, Chuck Cox, received a telephone call from Josh Powell, who informed him Susan was missing and that he was about to be interviewed by police again.

• Dec. 9 — Police served a search warrant on the Powell residence and removed boxes, bags and a computer.

• Dec. 10 — Law officers searched the Simpson Springs area but find nothing.

• Dec. 12 — Josh Powell, Chuck Cox, and other family gather outside the LDS Church's Hunter Central Stake Center to pray, sing hymns and start a 24-hour fast in hopes of her safe return. A tearful Josh Powell does not speak, but her Chuck Cox says he's concerned about the focus on his son-in-law. That evening, Josh Powell joins an effort to hand out missing persons fliers to Jazz fans attending a game.

• Dec. 14 — Josh Powell hired defense attorney Scott C. Williams and skips a third interview with West Valley City Police.

• Dec. 15 — Josh Powell provided a DNA sample to police.

• Dec. 17 — West Valley City police subpoenaed Salt Lake City television stations for footage of interviews with Josh Powell taken days after his wife's disappearance.

• Dec.18 — Josh Powell and his sons traveled to Puyallup, Wash., to stay in the home of his father, Steven Powell, for the holidays.

• Dec. 20 — Friends and family of Susan Powell hold vigils in Utah and Puyallup, Wash. to keep attention focused on finding her.

• Jan. 4, 2010 — Family and friends of Susan launched a social media campaign to spread word of the woman's disappearance on Facebook, Twitter and YouTube.

• Jan. 6 — Josh Powell and his brother, Michael, arrive at the Powell's West Valley City home to pack the family's belongings. Friends say Josh Powell, who has been fired from his job, may be unable to keep the home and is moving back to Puyallup.

• Jan. 27 — Neighbors decorate the Powell home in West Valley City with dozens of purple ribbons, hearts and signs to bring renewed attention to Susan's case.

• Jan. 28 — Josh Powell returns to West Valley City to make home repairs to his property to rent it.

• Jan. 29 — West Valley City police serve a search warrant on Josh Powell and seize the blue minivan he drove the night his wife disappeared to examine it.

• Feb. 15 — The Cox family holds a news conference in Puyallup, Wash. Family members allege Susan had a physical altercation with her husband and detail the couple's problems, citing controlling behavior by Josh Powell. They say Susan had suggested to family and friends she would end the relationship by their April 6 anniversary if the relationship didn't improve. The family also announced a nonprofit organization in Susan's name aimed at helping families of missing persons.

• Feb. 25 — Neighbors of Steven Powell cover their Washington neighborhood with missing persons posters and ribbons. The Coxes say it upsets the Powell children.

• April 10 — Volunteers search for Susan in the Simpson Springs area but turn up nothing.

• Aug. 25 — West Valley City police say detectives have spent at least 6,850 man hours to date searching for Susan, at a cost of more than $150,000. Five of the department's 28 detectives are assigned full-time to investigating Powell's disappearance.

• Sept. 10 — Chuck Cox and Ed Smart appear in Utah as part of an effort to raise awareness for kidnapped children and promote legislation that would require that DNA samples be taken from people arrested on suspicion of a felony.

• Dec. 6 — Josh Powell and his father, Steve, assert that Susan Powell ran away with missing Utah man Steven Koecher, who disappeared in Nevada in December 2009. The Powells claim the pair ran off to Brazil, where Koecher had served an LDS mission, where they may have married and started a new life.

• July 15, 2011 — Steve Powell says he will post portions of Susan Powell's childhood journals online.

• Aug. 18 — West Valley City police say there is a break in the case and that a search will be conducted in Ely, Nevada. Few other details are released.

• Sept. 13 — Investigators haul out bags and boxes of evidence from the home following a 9-hour search

• Sept. — Steven Powell revealed a romantic obsession with his daughter-in-law.

• Sept. — Steven Powell arrested for voyeurism

• Sept. 27 — Cox family gains temporary custody

• Feb. 1 — Judge denies Josh Powell custody

• Feb. 5 — Officials say Josh Powell and his sons are killed in an explosion inside Powell's Washington state home.