The Stay family is seen in this undated file photo.

HOUSTON (KABC) -- A man accused of shooting and killing six people, including four children, in suburban Houston was charged with capital murder Thursday.The charges come a week after the suspect allegedly taped his mother to a chair, choked her and threatened to kill her for speaking to his ex-wife, according to police records obtained by ABC News.Investigators say the victims knew their killer, he was their brother-in-law and uncle. Family members say they all grew up in Southern California together.Texas officials say Ronald Lee Haskell, 33, went to a home in North Harris County Wednesday evening, demanding the whereabouts of his ex-wife. Prosecutors say Haskell posed as a FedEx delivery driver and forced entry into the home, holding the children at gunpoint until their parents came home.According to prosecutors, Haskell was turned away by a teenager when he first went to the victims' home, but he returned a short time later, kicked in the door, tied up the family and then shot them in the head execution style when they told him they didn't know where his ex-wife was.Stephen Stay, 39, and his wife Katie Stay, 33, were killed, along with their two boys, 4-year-old Zachery Thomas and 13-year-old Bryan, and two girls, 7-year-old Rebecca and 9-year-old Emily. He also critically wounded 15-year-old Cassidy Stay, who told police she survived by playing dead after Haskell shot her in the back of the head. Cassidy remained hospitalized in critical condition on Thursday after suffering a fractured skull.The slain married couple and their children were Southern California natives and had lived in Moreno Valley before moving to Texas a few years ago, Stephen Stay's parents, Joyce and Thomas Stay, said. They live in the Sun City area of Menifee.Joyce and Thomas Stay know the family's killer since Stephen and Katie had both grown up with Haskell in San Marcos."How he changed, I just don't know, you just don't know what triggers that off in people's minds," Thomas Stay said in an interview with Eyewitness News.Deputies say Haskell and his ex-wife had battled through a nasty divorce, and say the domestic dispute, which resulted in a fatal shooting, could have been even worse. Police were able to intercept the suspect as he made his way to another home, where deputies say he was planning to shoot more relatives.Deputies say Cassidy called 911 and tipped off authorities that Haskell was behind the attack and was heading to the second location. Haskell was taken into custody after a chase and three-hour standoff with a SWAT team.Joyce Stay said she spoke to Cassidy on the phone from the hospital Wednesday night."I said, 'I'm so sorry Cassidy about everything that's happened, but I'm so thankful you're still here with us'. She said, 'My mom and dad are in a better place.'"Katie Stay's father, Roger Lyon, released a statement on behalf of his family praising Cassidy for her bravery and courage."We are grateful for this miracle. We are in awe of her bravery and courage in calling 911, an act that is likely to have saved all of our lives. She is our hero," the statement read.Haskell had a handful of previous run-ins with law enforcement in Utah, where he had previously lived with his ex-wife, Melanie Kaye Haskell. Neighbors said Haskell's marriage was so rocky that Melanie's sister, Katie, went to Utah last fall to help her sister escape the relationship and start a new life in Texas.In 2008, Haskell's ex-wife filed a domestic abuse complaint against her then-husband in Utah after he allegedly dragged her by the hair and repeatedly punched her in the head. The Logan City Police Department report states that she then decided to sleep in their children's bedroom, but he followed her in there and pulled her out of the room by her hair once more, continuing to punch her in the head.He was arrested on domestic assault and domestic violence in the presence of a child. He made bail and was released five hours later. Those charges were later dismissed as part of a plea deal.In July 2013, Melanie was awarded a protection order. She filed for divorce months later on Valentine's Day, and separated in June 2013. A judge granted joint custody of the couple's four children, ranging in age from 3 to 11, with Haskell's ex-wife getting primary custody.A representative for the Stay family says Haskell had been staying with his family in San Marcos, Calif. for the past few months. They heard he was allegedly distraught, suicidal and stayed in bed all day long. At one point, he allegedly told his ex-wife's sister, Katie: "I'll get even."On July 3, the suspect's own mother, Karla Jeanne Haskell, filed a restraining order in San Marcos against her son after he duct taped her wrists, tied her to a computer chair, choked her and threatened to kill her for speaking to his ex-wife."He yelled at me and twice placed his hands around my neck trying to choke me and caused me to pass out," Karla Jeanne Haskell, 61, said, according to the court documents. "He told me he was going to kill me, my family and any officer who stops him. He hid my telephones. I was taped up for four hours."There is no record of Haskell being arrested for the alleged assault on his mother. San Diego County sheriff's deputies say they conducted a background investigation on the suspect and his vehicle, but were unable to locate him. The Stay family's representative says his family lost track of him about a week ago.FedEx confirmed to ABC News that Haskell previously worked as a driver for the company but was employed by an independent contractor. He stopped working for the company in January."Our heartfelt thoughts and condolences go out to all those involved in this tragic incident," FedEx said in a statement.Haskell is being held without bail. He is scheduled to be arraigned on Friday.