Deputies with the Harris County Sheriff's Office responded to an incident at the 1800 block of Vernal Glen Circle.
Investigators said the mother shot her 6-year-old daughter before turning the gun on herself Monday evening.
Authorities said the mother was alone with her daughter at the time of the shooting.
'Mom's dead in blood': Teen to father after murder-suicide discovery
At the scene, Eyewitness News learned that two of her other children, a 13-year-old girl and a 16-year-old boy, discovered the bodies on Tuesday.
The oldest child, a junior in high school, called 911 and then his dad, who is the woman's ex-husband, asking to be picked up.
"Right now, I just don't know what's going to happen," the ex-husband said.
He told ABC13 that he is grateful his son is safe, but heartbroken for his son's half-siblings.
Editor's note: The original post stated the shooting happened in front of witnesses based off of initial information provided to ABC13.
WATCH: Sheriff Ed Gonzalez gives update after mom allegedly killed her daughter in front of 2 kids in apparent murder-suicide
Mom kills child in front of her 2 kids in alleged murder-suicide: HCSO