Josh Powell Planned Explosion, Attacked Sons

New details have emerged in the aftermath of the explosion that killed Josh Powell and his two sons.

Authorities now believe that Powell had been planning the explosion for some time, giving away his sons' toys days before their death. Detective Ed Troyer revealed that Powell took boxes of books and toys to a local Goodwill over the weekend, when he did not have custody of the boys.

Autopsies performed on the children reveal the grisly fact that Powell struck them with a hatchet before setting the home on fire. Authorities found the hatchet in the same room as the family and explained that the boys had markings on their bodies. That was not the cause of death, though, according to the medical examiner. All three Powell's died from carbon monoxide inhalation.

"I believe this was intentional -- it's two counts of murder and then suicide," said Det. Troyer. "Those boys were evidence. Those boys were going to be evidence against him." Family of the boys' missing mom, Susan, had told reporters that the boys were beginning to speak about what happened the night of her disappearance.

"They basically kept saying how they went on a vacation in the desert, and camping…they stopped at some place, and mommy and daddy left. Only daddy came back," explained Judy Cox, Susan's mother.

"I think it was more a case where he thought he was in a corner and didn't have a way of keeping the kids, and thought 'if I can't have them, nobody's going to.' I don't think he even thinks enough about anyone else to do it for revenge," family friend John Hallewell told ABC News.

"I am not able to live without my sons, and I'm not able to go on anymore. I'm sorry to everyone I've hurt. Goodbye," said Josh Powell in a voicemail to family. The message was left moments before the house exploded.

"We know where our daughter is, and we know that she's not here on this Earth…and that she's safe. And we know the boys are back with their mother, and that gives us a lot of strength," Susan's father told NBC.