ABC News said it obtained Tuesday what is believed to be Josh Powell's last words to his family before he struck sons Charles, 7, and Braden, 5, with a hatchet, then ignited a gas leak that exploded in his Puyallup, Wash., home his home Sunday.
The medical examiner said the three died of carbon monoxide poisoning, not the blast nor the hatchet cuts, and ruled the sons' deaths were homicides and Powell's death was suicide, CNN reported.
Powell left a voice mail for his family just 20 minutes before the carnage at his home began, ABC News said.
"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," the voicemail message said.
Powell was a suspect in the 2009 disappearance of his wife, Susan Cox, in Utah. Powell spoke with ABC News after a court hearing last week in which he was ordered to undergo psychosexual testing before he could regain custody of his sons, which he lost after pornographic images were found on a computer in his father's house, where they were living. The sons then moved in with their maternal grandparents and Powell was in a custody battle to get them back.
John Hallewell, who was Josh Powell's best friend, says Sunday's murder-suicide likely wasn't an act of revenge against the missing wife because Powell was too self-centered, ABC News reported.
"Josh has his problems, but he was trying to do what was right and start a family and do all those things … I think especially once Josh moved to live with his father, and he just got a hold of him, and basically he went downhill pretty fast from there," Hallewell told ABC News.
"I don't think it could have been for revenge," the friend said. "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."
Steve Downing, the lawyer for Cox's parents, said one of the sons had begun opening up about details of the night their mom disappeared, including an allegation she was in the trunk of the car and vanished soon after they arrived at a campground, ABC News said.
"They were beginning to verbalize more," Downing said. "The oldest boy talked about that they went camping and that mommy was in the trunk. Mom and dad got out of the car and mom disappeared."
Authorities said they believe that by torching his home, Powell not only killed his children but also destroyed evidence in the case of his wife, CNN said.
2014: The Year in Music [PHOTOS]