The shootings happened on August 20 at a mobile home park on the 4700 block of Anderson near Buxley in southwest Houston.
According to court documents, Francisco Arzate, 36, allegedly kicked his way into a mobile home where 63-year-old Guillermo Pineda Valdez and his wife, Maria, live with their daughters and grandchildren. Maria told police Arzate yelled in Spanish, "You are all going to die tonight!"
Arzate allegedly opened fire and shot the grandfather several times. He died at the scene, officials said.
He then shot the grandmother several times and fled. She was taken to Ben Taub General Hospital in critical condition and survived her injuries.
According to officials, Arzate is the ex-husband of one of the Valdez's daughters. They had been married about nine years.
Police are still looking for Arzate. He is charged with capital murder.
Anyone with information on his whereabouts is urged to call Crime Stoppers at 713-222-TIPS. All tipsters remain anonymous and could be eligible for a cash reward.