In a horrific twist of events, Josh Powell, husband of a Utah woman missing since 2009, killed himself and the couple's two sons Sunday, not long after he sent a cryptic message to his attorney stating I'm sorry, goodbye.

A couple of hours after Powell sent his lawyer, Jeffery Bassett, that message an explosion in Powell's Washington state home killed him and his two sons.

According to Fox News, authorities in Washington state said Powell's sons suffered severe chopping injuries to their heads or necks as they died in a house fire set by their father.

The Pierce County Medical Examiner's Office stated that the primary cause of death for Powell and his two sons was smoke inhalation, but the chop injuries also contributed to the boys' deaths.

According to timesunion.com, Charles, 7, was struck on the neck, and Braden, 5, suffered injuries to both his head and neck.

The boys were living with their maternal grandparents, who had been granted temporary custody after Josh Powell's father, Steve Powell, was arrested for child pornography and voyeurism. Before the boys' maternal grandparents were granted temporary custody, the two boys and Josh Powell had been living with Steve Powell.

On Sunday afternoon Powell's two sons were dropped off at their father's residence by a social worker with Child Protective Services for a supervised visit. The boys ran into the home but Josh Powell then blocked the social worker from entering. The social worker smelled gas and called her supervisor. Moments later the home burst in flames with Powell and his two sons inside.

Investigators searched the home Monday and found evidence showing Powell had planned on killing himself and his children. Two five-gallon gas cans were found inside. Pierce County Sherriff's Detective Ed Troyer said, This was definitely a deliberate, planned out event. Troyer also reported that a small ax was also found along the bodies.

Before the explosion Powell filed with a Washington state court to attempt to regain custody of his children.

A lesser person would fall under the intense scrutiny I am facing, but apparently my inherent resilience as a person makes it increasingly difficult for them to pursue their agendas, wrote Powell. I am standing tall for my sons, but it deeply hurts to face such ridicule and abuse.

The court ruled against Powell, ordering his children to remain with Susan Powell's parents, Chuck and Judy Cox, for the time being. Powell reportedly emailed his in-laws telling them that he could not live without his sons.

The Coxes told The Associated Press their grandchildren started telling them things about the night their mother went missing. Their attorney, Steve 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.

No other new information has turned up regarding the disappearance of Susan Powell. Last year Steve Powell claimed to have a flirtatious and sexual relationship with Susan. Susan's family has denied such claims, and Steve is currently a person of interest in Susan Powell's disappearance.