By the CNN Wire Staff
PUYALLUP, Washington — Three days after his young grandsons died in a fire police said was set by their father, Chuck Cox on Wednesday still was coming to grips with what happened.
Cox recalled the disbelief when he arrived at the smoldering ruins in Puyallup, Washington, on Sunday. Inside were the remains of the boys and their father, Josh Powell.
“I still couldn’t believe they could possibly be gone,” Cox said of his grandsons to HLN’s Nancy Grace on Wednesday night. “How could you do that to your children?”
Cox and his wife, Judy, recounted the incident and their previous suspicions that son-in-law Josh Powell was involved in the 2009 disappearance of their daughter, Susan Cox-Powell. The couple had custody of the children.
Services for 7-year-old Charlie and 5-year-old Braden Powell will be held Saturday, according to Anne Bremner, an attorney for the Cox family.
A social worker brought the boys to Powell’s home for a court-ordered supervised visit, authorities said. But as they approached the door, Powell pushed the social worker back, took the boys inside and locked the door.
“He blew up the house and the kids!” the social worker shouted in a 911 call released by Ed Troyer, spokesman for the Pierce County Sheriff’s Department.
Powell took the children and slammed the door in her face, she said. “I thought it was a mistake. I kept knocking and then I called 911.”
The powerful blast shook houses, with debris landing on lawns blocks away.
Minutes before he wounded his two young sons with a hatchet and set his house ablaze, Powell left a last voice mail to family members.
“I am not able to live without my sons, and I’m not able to go on anymore,” he said, according to ABC News, which obtained the voice mail. “I’m sorry to everyone I’ve hurt. Goodbye.”
Chuck Cox told HLN’s Grace the social worker should not have been taking the boys to Powell’s residence alone.
“I’m glad she is safe,” he said. “She could very well have been in that house. He could have closed the door behind her.”
Powell, who had not been arrested or charged, was embroiled in an ugly custody dispute with the Cox family.
Judy Cox said her grandsons wanted to stay at the Cox home and play with a young cousin rather than go to Powell’s home Sunday.
“They were just having a fun time playing together,” she told HLN. “They just didn’t want to leave. I reminded them that they would be able to play with him once they got back, which was a three-hour visit. But that didn’t happen.”
Investigators found the hatchet they believe was used on the boys in Powell’s home, said Troyer. Authorities believe Powell set an explosive fire there after wounding the boys Sunday afternoon.
Autopsies showed his sons suffered “chop” injuries to their necks, but both boys and their father died from inhaling carbon monoxide, the county medical examiner’s office said.
There has been some criticism of the 911 operator’s responses to the social worker. Troyer said he wished the operator’s “etiquette” would have been different, but information-gathering on such calls can take time.
The saga began two years ago in the Salt Lake City suburb of West Valley City, Utah, when 28-year-old Cox-Powell disappeared.
The deaths of Powell and the children could mean Cox-Powell’s disappearance might never be solved.
Still, the case remains open and investigators vowed to pursue it until the point of closure.
“I promised the Coxes I wasn’t giving up, and I’m still not because we want to get some closure here,” West Valley City, Utah, Police Chief Buzz Nielsen said Monday. “The case is still active; we’re not closing the case. We still got things that have not been resolved.”
Cox-Powell’s sister, Denise Cox, told CNN on Tuesday she had been told by her family that Powell could be arrested within a few weeks and that authorities were attempting to build a case against him despite the lack of a body.
“We were all excited that something was going to happen,” she said, adding the family was hoping that a deal could be made or Powell could be coerced to divulge his wife’s whereabouts.
According to investigators, Powell had said the last time he saw his wife was the night he and his sons — then ages 2 and 4 — left to go camping after midnight in freezing weather.
The double homicide and suicide on Sunday came days after a judge refused Powell’s petition to regain custody of his children. The judge instead ordered Powell undergo psychological evaluations — an order that came after authorities turned up child pornography in the home Powell shared with his father, Steven Powell.
As part of the investigation into Cox-Powell’s disappearance, a search of the home was conducted last year. During the search, investigators “discovered numerous images and recordings of adult and juvenile females,” according to a statement released by the Pierce County sheriff’s department.
Steven Powell was subsequently charged with 14 counts of voyeurism and one count of possessing images of children engaged in sexually explicit conduct, according to court documents.
After the arrest of Powell’s father, custody of his sons went to the Coxes, according to Washington state court records. Powell maintained in court documents filed last week that he established his own home after his father’s arrest and had “consistently proven my fitness as a stable and loving parent under close supervision by (child welfare caseworkers).”
Chuck Cox said he tried to prevent the visitation.
“We had warned the police… everybody, that he (Josh Powell) was capable of hurting those children and we were very concerned.”
But, apparently, the law allowed for it, Cox told Grace. “I don’t think we could have done anything more.”
The grandfather restated his belief that his son-in-law, who he described as very controlling and unlikeable, is responsible for Susan’s disappearance.
According to the Chuck Cox, Josh Powell bristled when he heard or saw evidence of the boys being close to their grandparents.
The Coxes said the boys at first would not talk about their missing mother, but then opened up a little bit.
One said he last saw her on a camping trip, Chuck Cox told HLN. But then they would forget details or not want to talk about her.
“They went back to a trained and coached response,” the grandfather said. “Josh didn’t want them saying anything about it.”
CNN’s Thelma Gutierrez, Ashley Hayes, Tina Burnside, Sara Weisfeldt and HLN’s Alexis Weed and Phil Rosenbaum contributed to this report.