SPOKANE, Wash. -

A jury heard opening statements Wednesday in the trial of a decorated Iraq War veteran accused of killing his estranged wife's mother, stepfather and brother.

Roy H. Murry is charged with three counts of premeditated first-degree murder with aggravating circumstances.

Firefighters were first called to fire at a Colbert home in May 2015. Inside the burning home, they found he bodies of "Terry" Canfield, a Spokane firefighter, his wife Lisa and her 23-year-old son John Constable. They had been shot multiple times.

Prosecutors say it was a well-planned ambush, but defense attorneys insist Murry is not responsible.

Spokane County prosecutors lack a lot of the traditional evidence you might see in a homicide trial. Wednesday in court, they admitted to the jury that they don't have the murder weapon and don't have any DNA that ties Murry to the killings.

In opening statements Wednesday, chief deputy prosecutor Jack Driscoll laid out a pending divorce as Murry's motive for the crimes.

"Amanda Murry knew that she could not be the one to ask for a divorce. She was too concerned about how her husband, Roy Murry, would react if she did," Driscoll said in court.

Prosecuotors argue Murry reacted to a possible divorce by torching Amanda's parents' home just hours after the pair agreed their marriage was over.

Amanda Murry, who also lived in the home, had volunteered to work an overtime shift that night and got home three hours late.

"She ran up to a fireman saying, 'This is my mother's house.' She was then told a woman's body had been pulled from the fire and was deceased. Amanda Murry, dressed in her scrubs, collapsed right there in a puddle of water," Driscoll said.

Amanda told investigators she suspected her estranged husband was the killer.

Investigators later found the bodies of Amanda's stepdad and little brother. They said .22 shell casings littered the crime scene, the same brand and caliber of ammunition later located in Roy Murry's car.

"You will hear what was found in the terms of evidence," Tom Krzyminski, Murry's public defender, said. "But you also will hear what was not found. What was not found is evidence that Roy Murry was at the house."

Krzyminski also told the jury that when his client was contacted by police in Lewiston later that morning, he appeared to be well rested, did not have any obvious injuries and also did not smell like someone who had set a pair of gasoline-fed fires.

Investigators said Murry handed over a pair of cell phones to Lewiston police that morning. They said he used a map to show Spokane County investigators how he would have ambushed Amanda's family, but also said he felt the Russian secret police were really behind these murders and that Amanda was a spy.

Amanda finalized her divorce proceedings Tuesday and will soon take the stand against her ex-husband.

Murry was awarded the Bronze Star while serving in the Iraq War. Court documents show he came home with severe PTSD.