GRAHAM, WA (CBSNewYork) — Susan Powell made national headlines when she vanished, now her husband and two children are dead in an explosion that seems to have been intentional.

“I ran outside and the whole house was on fire,” said neighbor Ryan Mickle.

Cell phone videos show flames raging through the Graham, Washington home after it blew up. Inside police found the husband and two sons of Susan Powell, a mother who vanished in Utah in 2009.

Police say that Josh Powell used may have used accelerants to fuel the flames.

“By the information that we’ve gathered, the actions of Josh, and how fast this fire was burnt, we believe it was intentional,” said Sgt Ed Troyer.

The home exploded moments after a social worker brought 7-year-old Charles and 5-year-old Braden for a supervised visit with their father.

Police say that Powell blocked the worker from getting into the home and that the house went up in flames before help arrived.

“If you have someone who is hellbent on doing what he’s going to do, which was the double homicide of the two boys, there is not a lot that you can do to stop him,” said Sgt Troyer.

The boys had been in the custody of their maternal grandparents.

Last week Josh Powell pleaded with a judge for custody of his sons, saying that he had proven himself a fit and loving father. The judge denied his request.

Friends of the family say that Josh was clearly affected by the judge’s decision.

“We knew that Josh must be completely furious that control was taken away. We knew he must be planning something, but we had no idea he would do this,” said Kiirsi Hellewell.

Authorities announced on Monday that Powell had been planning the explosion for a while. They say that he sent final emails to multiple people  including one to his attorney that said, “I’m sorry and goodbye.”

Steven Downing, an attorney for Susan’s family says that the two boys began opening up about the night that their mother vanished, and that their story poked holes in their father’s alibi.

“They had gone camping, their mother had been in the trunk and later their mom and dad walked out into the desert and mommy got lost,” he said.

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