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Houston-area law enforcement on Thursday released a sketch of a man believed to have opened fire into a car Sunday morning, killing a 7-year-old girl.

"We're not going to rest until we find justice for Jazmine,” Harris County Sheriff Ed Gonzalez said at a press briefing Thursday.

Jazmine Barnes, 7, was fatally shot Sunday morning after a gunman described as a white man possibly in his 30s or 40s opened fire on the car she was riding in with her mother and siblings on the way to a store at around 6:50 a.m., the sheriff's office said.

The family is black, and the shooting has raised fears among some in the community, including the mother, that it may have been racially motivated.

An unsolved 2017 shooting around 6 miles away also involved a white suspect and a black victim who survived, but so far no direct connection has been found between the cases, the sheriff said.

Gonzalez on Thursday referenced those concerns, and said "we're not tone deaf to the concerns of many in communities of color that feel that maybe they could be targeted — it's a reality that it does happen, it could happen."

This sketch released by the Harris County Sheriff's Office shows a man witnesses say murdered 7-year-old Jazmine Barnes on Dec. 30. HCSOTexas

He said the focus now is identifying the shooter, "this coward," who killed Jazmine, and finding the pickup truck he was driving.

"We're also working on every other lead we can develop, including previous cases," said the sheriff, who previously called the shooting "unprovoked and senseless."

The sheriff’s office on Thursday also released new surveillance video from a nearby business showing the red truck believed to have been driven by the gunman.

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Earlier Thursday, Jazmine’s mother, LaPorsha Washington, told reporters that she believes the shooter will turn himself in.

"His conscience is finally going to get to him," LaPorsha Washington, who was also shot, said. "After he sees my child’s face go across his TV so many times, he's going, he’s going to turn himself in."

Jazmine’s 6-year-old sister was injured by shattered glass in the shooting.

Lee Merritt, an attorney assisting the family, disputed earlier reports that the suspect had a beard, saying Thursday that there may have been stubble but no beard.

Jazmine’s 15-year-old sister, who was in the car at the time of the shooting, told reporters Thursday that the gunman was white with blue eyes and was wearing a hooded sweatshirt. "I couldn't see his hair, nothing like that," she said.

Do you recognize this truck? This is the truck of the suspect who fatally shot 7-year-old #JazmineBarnes. If you have any information call 713-221-6000 or @CrimeStopHOU at 713-222-TIPS. #HouNews #JusticeForJazmine pic.twitter.com/8IKFb4SJ3S — HCSOTexas (@HCSOTexas) January 3, 2019

The mother said she and her children did nothing to provoke the shooting, and that she believes it could possibly be a hate crime.

She said she didn’t know how many shots were fired, "but I know he finished his clip" and that "he emptied out his gun; I know that for a fact."

Gonzalez said Thursday that investigators are taking a second look at the unsolved 2017 shooting.

"We're not prepared to say that there's no connection, but also being very careful. We haven’t found a direct connection at this point," Gonzalez said. "But I just want to be cautious and not startling folks and believe that there’s necessarily a serial shooter out there," he said.

The killing has prompted an outpouring of support, and a reward of $100,000 has been raised in an effort spearheaded by civil rights activist Shaun King.

Jazmine Barnes, 7, was fatally shot in Harris County, Texas, on Dec. 30, 2018. Family photo

NBA great Shaquille O'Neal and a Houston police officer have also stepped in to cover the costs of the funeral.

NBC affiliate KPRC of Houston reported that O’Neal and Houston Senior Police Officer Kenneth Miles dropped off a cashier’s check to cover the costs of Jazmine’s funeral, which is scheduled for noon Tuesday at Green House International Church.

Miles told the station that O’Neal was in Houston and the two men decided to step in and help. "You can just imagine if one of your children or loved ones were the victim," Miles told the station.

Houston Texans star wide receiver DeAndre Hopkins said on Twitter on Thursday that he would be pledging his playoff check to support Jazmine’s family.

"When I see Jazmine Barnes' face, I see my own daughter. I'm pledging my playoff check this week to help her family with funeral costs," and to support the reward, Hopkins, 26, wrote.

"It's the least I could do was help out," Hopkins told reporters Thursday in video posted on the team’s website. "I have a 5-year-old daughter ... That could have been anybody in that position on this team."

He added, "it could have been, you know, anybody, you know, who's in this city. So, it's just unfortunate."