HOUSTON, Texas — Ronald Lee Haskell Jr. has been sentenced to death in the fatal shooting of six members of his ex-wife's family in 2014 — which included the execution-style killing of the four of the family's children, according to prosecutors.

Prosecutors say Haskell, of Utah, traveled from California to Texas on a mission to kill anybody who helped his ex-wife, Melannie Lyon. The couple had recently divorced after more than a decades-long abusive relationship.

Haskell spent months planning the murders and two days in the Spring, Texas, area stalking the Lyon and Stay family, according to prosecutors.

On July 9, 2014, he disguised himself as a FedEx delivery driver and made his way into the Stay residence in Spring, Texas. There, prosecutors say he held five of the Stay children hostage at gunpoint until the parents, Katie and Stephen Stay, arrived, forced them all to the ground, and shot them one-by-one. Katie, who was Lyon's sister, Stephen, and four of their five children; 4-year-old Zach, 7-year-old Rebecca, 9-year-old Emily, and 13-year-old Bryan, were killed.

The fifth child, then-14-year-old Cassidy Stay, survived the shooting despite being shot in the head by playing dead. Now 20, she testified in the case against Haskell.

"I hope that when you die, you will get the punishment you deserve from God," she told Haskell at sentencing.

After the fatal shooting at the Stay residence, Haskell had reloaded his gun at started for Lyon's parents and brother's residences — but was stopped and arrested before arriving. Law enforcement commended Cassidy in preventing further killings, despite her injuries.

"After the murderer left, Cassidy’s quick actions prevented Haskell from carrying out the remainder of his plan to kill 22 members of his ex-wife’s family," read a statement from the Harris County District Attorney's Office.

Haskell's defense attorney's argued he should be found not guilty by reason of insanity. At sentencing they shifted to life behind bars without a death sentence arguing Haskell suffered from several mental illnesses.

Prosecutors rebutted, stating Haskell was a vengeful, manipulative liar who, upon expert witness testimony, faked his mental illnesses.

A jury rejected Haskell’s insanity defense Sept. 26 and found him guilty of capital murder. He was sentenced on Friday, October 11, 2019.

“The death penalty is only for the worst of the worst,” stated Harris County District Attorney Kim Ogg. “Haskell meticulously planned and carried out the slaughter of the Stay family and the death sentence handed down by a jury of his peers is appropriate.”