A California man accused of driving across the country to kill six of his ex-wife’s family members in a “cold-blooded execution” fueled by revenge was found guilty of capital murder in a Texas court on Thursday.

Ronald Lee Haskell, 39, now faces the death penalty for the July 2014 massacre of Katie Stay, 34, her 39-year-old husband, Stephen, and four of their five children inside their suburban Houston home.

The only survivor of the bloodbath, 19-year-old Cassidy Stay, who played dead after Haskell shot her in the head, cried in the courtroom’s front row along with several family members as the verdict was read.

“This was anger, rage. This was vengeance and it was not a serious mental illness,” Harris County Assistant District Attorney Samantha Knecht said in court, adding that he was “not a disorganized, psychotic individual. That is a man with a plan.”

Throughout the month-long trial in Houston, prosecutors argued Haskell had been planning for months to drive from California to Texas to carry out the execution, motivated by his desire to hurt anyone who helped his ex-wife, Melannie Lyon, after their acrimonious divorce.

“He absolutely knew what he was doing that day,” Knecht said during her closing arguments Wednesday. “He took steps to hide, to disguise, and to plan this execution.”

Haskell’s defense attorneys did not deny the 39-year-old committed the crime—but argued that he was driven to kill by his mental-health problems and the voices in his head.

“He had a severe mental illness,” defense lawyer Douglas Durham said. “Don’t let yourselves get angry or become vengeful yourself for the terrible, terrible acts of Ronald Haskell.”

Prosecutors argued against his insanity defense, pointing to Haskell’s planning of the crime, including his purchase of a FedEx uniform to wear as a disguise to gain access to the Stay family’s residence. Haskell also allegedly made a pit stop in Utah to steal a gun from his ex-girlfriend, and then purchased over 200 rounds of ammo.

Haskell stalked the Stay home for days, prosecutors said, before finally knocking on the door dressed in his FedEx outfit on July 9, 2014. Cassidy Stay, who was then 15, testified in court that she opened the door and told Haskell her parents were not home but she expected them to return in an hour.

“He puts on this FedEx shirt, this disguise. If he didn’t know what he was doing was wrong, why did he need a disguise?” Knecht said.

The 39-year-old left but later returned and forced himself inside the house. Cassidy Stay testified that she was tied up and held at gunpoint with her siblings until her parents arrived.

“I felt like the light got sucked out. I started to get nervous,” Stay told jurors. “I said please don’t hurt us, please don’t hurt us. I knew how dangerous he was.”

“I went through and told him my brothers and sisters names and ages. I was appealing to his humanity. I didn’t think someone would hurt kids if they knew how old they were,” she added.

The teenager said they were all told to lie in a row, then Haskell began counting to seven before shooting them in the head. Katie Stay lunged at him, prosecutors said, when he shot her in the face with a makeshift silencer over his weapon.

“I saw her fall. I started screaming, I heard Zach screaming. I heard another shot and then Zach stopped screaming,” Stay testified.

Stay said she played dead alongside her fatally shot father, Stephen Stay, her brothers Bryan, 13, and Zach, 4, and sisters, Emily, 9, and Rebecca, 7.

When he’d finished shooting, Haskell fled and Stay called police, telling them “Uncle Ronnie” was heading to her grandparents’ house. Several officers caught up with Haskell near Lyon’s parents’ home and arrested him after a standoff.

Melannie Lyon, 38, told jurors that Haskell had often threatened to harm her and her family if she told anyone about his physical and emotional abuse—and instantly knew it was her ex-husband when she heard her family members had been murdered.

“He had carried through on his promises to make me watch my family die,” Lyon said.

The mother of four spoke about the abuse she endured during her 12-year marriage to Haskell, who isolated her from her family and threatened to kill her if she left.

In 2008, Lyon said she finally reported her husband’s abuse, at which point he pleaded guilty to a misdemeanor and was granted nine months probation. Five years later, she said she reached a breaking point when her husband punched her during a fight about flooring for their new Utah home.

“That was my wake up call,” Lyon said. “I knew I could not raise my kids in this evil environment any longer.”

When Haskell was at work, she took their kids and stayed at a shelter for five weeks while she filed for a protective order. Lyon said her sister Katie came up to help her leave Utah. At one point, Haskell allegedly threatened Katie during a conversation with his oldest son, saying, “If she’s there helping you and helping your mom, I will make her pay.”

Haskell’s defense attorneys said that while Lyon’s decision to divorce him caused him to spiral, it was the voices in his head that urged him to kill the Stays so his marriage could be saved.

“He tried to get help for years. He didn’t want to be this way. He had no control,” Neal Davis, another defense attorney, said.

Forensic psychiatrist Stephen Raffle testified that at the time of the killings, Haskell was suffering from a form of bipolar disorder and schizoaffective disorder, a condition characterized by hallucinations or delusions.

Raffle said the voices in Haskell’s head “had basically taken control” of him, adding that one “voice name Joseph was telling Ron that he has to kill members of his ex-wife’s Melannie’s family in order to get reunited with her.”

Lyon dismissed those claims, stating that during their marriage, her ex-husband had been diagnosed with depression and that he had abused his medication.

“He used his health in any state as kind of a feather in his cap as an excuse for his behavior,” she said, adding that he never spoke about delusions or hallucinations.