According to the Harris County Sheriff's Office, it happened after 9 p.m. on Normandy near Woodforest.
Investigators said the ex-husband was dropping off a child with his ex-wife when the two adults got into an argument. That's when the woman's current husband intervened and things got physical between the two men.
The woman's husband pulled out a gun and started shooting at the ex-husband, killing him.
Deputies said it will be up to a grand jury to decide if any charges will be filed.