Houston police have launched a massive manhunt after a seven-year-old girl was fatally shot in a Walmart parking lot.

Jazmine Barnes was killed around 7am on Sunday in a car alongside her mother and three sisters as the car exited the Walmart on Wallisville Road in northeast Houston.

Police said that some kind of altercation in the parking lot may have led to the shooting, and the gunman fired into the vehicle holding the five females, killing the girl and injuring the woman in her arm.

The shooter is described as a white male with a beard in his 40s, driving a red pickup truck.

The shooter pulled alongside the mother's car (pictured) and fired into it, killing the girl. The mother managed to flee the scene in her car and came to rest on a highway median

Image courtesy ABC13

Police said the shooter pulled his truck up alongside the woman's car and fired into it, killing the girl.

The woman driving the car was struck by gunfire in the arm and wounded.

Another girl aged about ten was non-seriously injured by flying glass. Two teenage girls who were riding in the car were not injured.

The woman driver, possibly in a panic, was able to flee the scene in her car, racing onto the nearby Belt Parkway before coming to rest on the median.

Harris County Sheriff's Office Major Jesse Razo (above) urged the gunman to surrender

At a media briefing, Harris County Sheriff's Office Major Jesse Razo advised the public that the killer may confide in someone about the crime, and urged anyone with information to come forward.

He also made a direct appeal to the gunman to surrender.

'We're going to use all resources available to bring this killer to justice, and I urge you, whoever did this, you know who are, please turn yourself in now,' Razo said.

'Because we will be looking for you. We will locate you, we will find you,' he added.

Anyone with information about the suspect is urged to call Houston CrimeStoppers anonymously at 713-222-8477 for a potential cash reward.