The attack happened around 3 p.m. in the 300 block of North Vista, according to the Harris County Sheriff's Office.
Family identified the victim as 32-year-old Ashanti Hunter.
"Why? Why? Why? I just want to know why," said Hunter's cousin, Myriane Rodrigues.
Rodrigues said she had just returned to the apartment complex to bring Hunter's three children back from a sleepover. The kids ran back out of the apartment and said their mother was in the middle of an argument with her boyfriend.
She ran for help.
"Knocking on everybody's door. Nobody answered their door," Rodrigues said.
Then, she heard gunfire.
"I heard gunshots and it was my cousin in my passenger seat," Rodrigues said, through tears.
Hunter's boyfriend, who has not been identified, is in custody.
Her family members said she had been in a relationship with her boyfriend for about five years. They are still trying to figure out what the argument may have been about.
"I wish I could have been here to get her from it. I wish I could have been here, Lord," added Rodrigues.
Hunter's children are now in the care of extended family.
Report a typo to the ABC13 staff