HOUSTON — Five years after the execution-style murders of a Spring couple and four of their five children, Ronald Haskell is on trial for capital murder. 

"This was a plan that was created in anger and fueled by vengeance," said prosecutor Samantha Knecht. 

Haskell sat stoic in the courtroom as prosecutors laid out their case detailing the horrific events of July 9, 2014.

Court records show Haskell plotted the murder spree because his in-laws had encouraged his wife to leave him. 

Ronald Haskell_15359659
Ronald Haskell appears in court.

"He was mad," said Knecht. "He was angry. He had lost control and he didn't like it. He vowed he was going to hurt anyone that helped Melanie."

RELATED: Court records reveal Haskell planned and plotted shooting rampage

RELATED: Timeline of mass shooting in Spring

Prosecutors say Haskell drove from Utah to Texas, broke into Katie and Stephen Stay's home and held the couple and their five children at gunpoint.

"Katie in her wisdom and maternal instinct knew what was going to happen," said Knecht. "She jumped and screamed 'no' and went at the defendant. He pulled the trigger and shot Katie in the face."

The others were tied up and shot execution-style, according to prosecutors.

Investigators said the couple's 15-year-old daughter, Cassidy, suffered a bullet fracture to her skull. She played dead until the Haskell left.

"She's screaming and she gets hit in the head," said Knecht. "She can hear Zach crying. She can hear the shooting continue down the line. Emily. Bryan. And then another shot and Zach stops crying."

It was Cassidy who alerted authorities that the gunman was on his way to her grandparents home to kill more relatives. 

Deputies arrested Haskell outside the home of his wife's parents. They weren't harmed.

The jury reviewed crime scene photos and listened to Cassidy's harrowing 911 call. That call was credited with saving lives before Haskell could kill her grandparents. 

 Cassidy is expected to be the star witness in the trial testifying against her uncle. She could take the stand as early as tomorrow.

"He tried to take out their whole family," said Knecht. "We are confident when you listen to the whole evidence there will be one result, that he is guilty of capital murder."

Defense attorneys will argue an insanity defense. They say Haskell has a history of mental illness. They say Haskell suffered from hallucinations and that he kept hearing two male voices in his head.

"What is chilling is 'Jonathan' and 'Joseph' tell Ron that he needs to kill the Stay family," said Doug Durham, Haskell's defense attorney.

Haskell's defense would not answer whether their client is remorseful. They say he's still undergoing psychotropic treatment at the jail.

"When you start comparing details of this plan, you'll see it's not rational. It's psychotic, and it'll bear out in our case. 

The trial is expected to last two months.

ALSO POPULAR ON KHOU.COM