The social worker had brought Charlie, 5, and Braden, 7, to the house for their court-ordered supervised visit on Sunday. She frantically called for help as soon as she said Powell took the children and shut christian louboutin her out of the house.
"Nothing like this has ever happened before, I'm really shocked, I can hear one of the kids crying," the woman said. "This is the craziest thing, he looked right at me and closed the door."
Concerned that the children might be in a life-threatening situation, the woman also told dispatchers she smelled gas coming from the house. After the house exploded in flames, she called again.
"He blew up the house and the kids!" she cried. "He slammed the door in my face!"
Excerpts from the call were obtained and broadcast Tuesday night by Wash. NBC affiliate, KING5.
It also spoke to the husband of the un-named social worker, who said she was "not doing very well" despite being offered counselling.
He told the station she was "devastated and traumatized" by the episode and had worked with the boys for a long time, forming a bond with them.
The husband, who was also not named, told KING5 she made a distraught call to him after the fire, repeatedly saying about the boys: "They trusted me, they trusted me."
The double murder-suicide took place days after Powell, whose wife Susan went missing in 2009, was ordered to undergo a psycho-sexual evaluation as part of a bid to regain custody of his children from his in-laws.
Report: Powell left apologetic voicemail minutes before death
Authorities in Wash. and Utah, from where the family moved, are now effectively treating the disappearance of Susan Powell as murder, even though her body has yet to be found.
MSNBC's Thomas Roberts talks to Chuck and Judy Cox, parents of Susan Powell, about their grandsons' deaths and their Christian Louboutin Flats daughter's disappearance.
Salt Lake County District Attorney Sim Gill acknowledged for the first time that investigators believe Powell is likely dead, but he said in an interview with the AP that the case remains a missing persons probe for now.
"I think when I talk about it as a missing persons case, that's because we haven't located the body of Susan Powell," Gill said. "Do we think that she may have met harm? Sure. I think that's been an ongoing assumption with law enforcement."
Investigators said Josh Powell withdrew $7,000 in cash from a bank the day before he killed himself and his two young sons in the house fire.
Pierce County Prosecutor Mark Lindquist said detectives obtained Powell's bank records Monday, and on Tuesday they searched a storage unit he rented. It isn't clear what happened to the money.
Josh Powell claimed that on the night Susan Powell vanished, he took Charlie and Braden from their then home in West Valley City, Utah, on a late-night camping trip. Authorities eventually searched the central Utah desert but found nothing.
Susan Powell's father said that when police went to the family home after she was reported missing, they found a wet spot in the house being dried by two fans. Police have not commented further on what they found.
Last September, authorities got a warrant to search the home of Josh Powell's father, Steve. Josh Powell and his sons were living there at the time. The documents obtained by the AP did not specify a suspect.
In addition to the charges, the warrant listed Steve Powell's work laptop computer as well as cars that he used.
Authorities found explicit Christian Louboutin Studded Pumps images on his computers during the search, and he was jailed on voyeurism and child porn charges. The boys were later sent to live with Susan Powell's parents.