Ronald Lee Haskell, 33, has been charged with six counts of capital murder. He allegedly shot Stephen Stay, his wife Katie and their five children in the head Wednesday after tying them up and trying to get them to reveal his ex-wife's whereabouts.
One of the children, identified by neighbors as Cassidy, 15, survived. She told police that Haskell was headed to the home of another family where he planned similar violence.
"She was able to play dead until he left. She called 911, and the police arrived," investigators said in court documents.
Police said Haskell was wearing a FedEx driver's uniform when he entered the Stays' home in Spring, a Houston suburb.
Mark Herman, a police spokesman, said Cassidy probably saved lives. Police intercepted Haskell at the other house, and he surrendered after a brief slow-speed chase and a standoff lasting several hours.
Police in Utah said Haskell had been arrested there in 2008 for an alleged assault on his wife and in 2013 for allegedly violating a protection order.
Cassidy allegedly told police that Haskell, pretending to be making a delivery, knocked on the door twice asking for her parents, who were not home. On his third try, he gave his name, which she knew, and then forced his way into the house, she said.
According to investigators, Haskell then tied the children up and waited for the parents to return.
Neighbors identified the other children as Bryan, 13, Emily, 9, Rebecca, 7, and Zach, 4.