HOUSTON — A man in a pickup truck pulled up next to a car that was leaving a Houston-area Walmart parking lot and started shooting, killing a 7-year-old girl inside the car and wounding the girl's mother, authorities said Sunday.

Three other girls were in the car, but it wasn't immediately clear if they also are related to the woman, who authorities say was shot in the arm.

Jazmine Barnes, 7, was fatally shot in a Walmart parking lot in Harris County, Texas, on Dec. 30, 2018.

Harris County Sheriff Ed Gonzalez said in posts on Twitter and Facebook that the girl who died was 7-year-old Jazmine Barnes. He said her mother, 30-year-old LaPorsha Washington, was wounded but survived her injury.

It wasn't immediately clear what prompted the Sunday morning shooting. An arrest hadn't been made as of Sunday night.

The red pickup fled the scene after the shooting. The car also sped away before it came to a stop and the woman called 911, authorities said.

Sheriff's Maj. Jesse Razo said the other girls who were inside the car when the shooting happened were "shaken" and "devastated."

"We're going to use all resources available to bring this killer to justice," Razo told reporters at the scene. "And I urge you, whoever did this, you know who you are, please turn yourself in now because we will be looking for you, we will locate you, we will find you."