The sons of missing mom Susan Powell suffered neck and head injuries at the hands of their father, Josh Powell, before dying in the house he set on fire. NBC’s Miguel Almaguer reports.
>> details in the double murder -suicide of josh powell and his two young sons. we should warn you these details are disturbing. we will talk to susan powell 's parents in a moment, but first nbc's miguel almaguer joins us from washington with the latest on the story. miguel, good morning.>> reporter: ann, good morning. police are working to retrace josh powell 's steps in the days leading up to the fire. they say when a social worker brought his kids here he certainly had a plan -- to kill his children. the house went up in flames moments after powell 's two young sons arrived with a social worker for their scheduled visit. a neighbor captured the aftermath in this home video .>> reporter: firefighters put out the blaze but had no chance to save 7-year-old charlie and 5-year-old braden, the powells' young boys .
>> reporter: police say powell opened the front door, let the boys inside and blocked the social worker from entering, slamming the door in her face. she called the supervisor, said she smelled gas in the home. moments later an intense, fast-burning fire raged.>> why couldn't he just do that to himself, you know? why would he have to take those babies with him?>> reporter: in september powell lost custody of his sons a month after arrest of his father steven on charges of voyeurism and child pornography . in steven's home they also found illicit pictures of susan cox powell , photos taken years earlier without her knowledge.>> reporter: despite powell 's emotional appeal to a judge the boys were placed in the care of his missing wife's parents -- chuck and judy cox. too distraught to be interviewed sunday in a statement they said words cannot adequately express the grief. first susan and now charlie and braden. josh powell always denied any involvement in his wife's disappearance. utah police called him a person of interest but never charged him with a crime. susan cox powell vanished in december 2009 , the same night josh told police he took his boys on a late night camping trip in freezing temperatures. her body has never been found.>> reporter: according to police, powell did exactly that, killing his children -- two innocent boys whose short lives had already been filled with incredible loss.>> reporter: and police say this murder-suicide was certainly well planned out. they say they found a hatchet on the scene, that it appeared josh powell injured his boys first before they ultimately died of smoke inhalation. they say they found ten gallons of gasoline in the home used to fuel the fire and powell sent out several e-mails, not only to family members but to a pastor to take care of some loose ends he apparently had left behind. ann?