(CNN) After 7-year-old Jazmine Barnes was killed , eyewitnesses said the suspect who suddenly opened fire on her mom's car was a bearded white man in his 40s, driving a red pickup truck.

Jazmine and her mom and sisters are African-American. As the case gained national attention, suspicion swirled that it was a racially motivated attack.

But when investigators identified a suspect on Saturday, he looked nothing like the initial composite sketch of the suspect created based on witness reports.

Eric Black Jr., 20, is African-American, and so is a second suspect, according to Harris County Sheriff Ed Gonzalez.

Attorney S. Lee Merritt, who is representing Jazmine's family, said her relatives welcomed news of the arrest -- even though the suspect's race came as a surprise.

On Sunday, authorities said the shooting was "likely a case of mistaken identity." The sheriff says that "it does not appear that (the shooting) was related to race."

In a week, the description of the suspect and the circumstances that may have led to her death changed.

Here are some factors that might explain why that happened.

The shooting happened quickly

LaPorsha Washington, 30, and her four daughters were in her car last Sunday, on a coffee run to a local convenience store. It was around 7 a.m., Washington said, and the girls were still in their pajamas.

Witnesses said that someone in a pickup truck pulled up alongside Washington and fired into her car, the Harris County Sheriff's Office said.

Washington's oldest daughter, Alexis Dilbert, was in the front seat. She told CNN last week she remembered making eye contact with a man who pulled up close to them. "His eyes were blue. His face was kind of thin and pale," she said.

Based on the family's description, investigators released a composite sketch of the suspect: He was white with a thin build, in his 30s to 40s, with a 5 o'clock shadow.

Gonzalez said he believes they were truthfully recounting what they remember. "This just went down very quickly when the gunfire erupted," the sheriff said.

Obviously, the men arrested don't fit the description of multiple witnesses or the sketch. Initially, this fact made it difficult to accept the tip that resulted in these arrests. However, if the confession obtained is reliable, There is likely an explanation for the confusion. pic.twitter.com/8vv1pUqfd0 — S. Lee Merritt, Esq. (@MeritLaw) January 6, 2019

Three of Washington's children -- Jazmine, a 6-year-old and a teenage daughter, were in the backseat, Washington said.

The sheriff said the shooting was traumatizing to the children.

"You're talking about small children. They witnessed something very traumatic. And it's very likely that the last thing they did see was ... indeed that red truck and that driver that was in that truck, and that's what they remembered last."

It was dark

Gonzalez said the shooting happened before the sun rose in eastern Harris County, and the darkness could also have impacted the eyewitness accounts.

"The sun didn't start to rise until about 7:15, 7:16 a.m. that morning, so it was still dark when all this happening," the sheriff said Sunday.

"So there are a lot of different facets that could potentially impact someone's memory of what they saw at that time."

A red truck happened to be there

Early in the investigation, Harris County investigators released a photo from surveillance footage of a red pickup. The sheriff urged the public to come forward with information if they "saw this red pickup truck speeding along the service road that morning."

Update on Wallisville: deceased child is 7 year old, may she Rest In Peace. Suspected shooter described as white male, 40s, a beard, driving a red truck. If you know anything please contact us asap. We need our communities help. cc: @CrimeStopHOU #HouNews — Ed Gonzalez (@SheriffEd_HCSO) December 30, 2018

Gonzalez said Sunday there was indeed a red pickup at the scene of the shooting. The driver had stopped at a traffic light with Washington shortly before the shooting started close to 7 a.m. The pickup probably entered the Sam Houston Tollway when the light turned green.

"We believe now that that red truck and the driver is most likely just a witness, either by sight or sound, to what actually transpired," Gonzalez said.

The sheriff said authorities would still like to speak to the pickup driver, who may be able to shed some light on what happened.

Witness accounts are often unreliable

At least four other witnesses also reported seeing someone in a red truck fire at the vehicle, Merritt said.

But witness accounts are inherently fallible.

"Generally speaking, when we're talking about these kinds of events, we're talking about something that happens quickly. It's unexpected," said Gary Wells, a psychology professor at Iowa State University who is an expert in eyewitness testimony. "The brain isn't really wired to record verbatim accounts of things but rather is wired only to record the gist of things."

That's especially the case in dangerous circumstances, he said.

"When we become fearful, all of our mental resources tend to go toward survival. That's why we duck, we run," he said. "None of our mental resources are really going to be forming long-term memories. It's not functional. What's functional for survival is to survive."

He said sketches are also unreliable and often lead law enforcement down the wrong path.

"When we see a face, we don't remember a face based on its individual features," Wells said. "We don't know the nose. We don't know the lips or the mouth or the chin or the eyes. ... We know the whole face as a whole."

Police were acting on the information they had

As tips poured in, investigators canvassed streets and tried to track down surveillance video, Gonzalez said. By the middle of last week, police received an anonymous tip that would redirect the investigation away from a white man driving a red pickup, Gonzalez said.

Gonzalez said that the tipster had approached writer and activist Shaun King days earlier, and King passed the tip on to police. King and Merritt helped raise a $100,000 reward for information leading to the suspect's arrest.

The tipster said Black and another person identified in court as "L.W." had mistaken Jazmine's family vehicle for another vehicle, the affidavit said.

The sheriff said the tip provided "a little bit of a different angle," and required further review. "We had some very basic information and it just didn't quite gel at the time," the sheriff said. Investigators followed up and began to develop the tip more, he said.

"It really came to head yesterday, and pieces started falling together very rapidly," the sheriff said Sunday.

Black was pulled over Saturday for not using his turn signal and was arrested for marijuana possession, according to a affidavit read in court.

Eric Black Jr., 20, is charged with capital murder in the death of 7-year-old Jazmine Barnes. #hounews pic.twitter.com/OlmqMlb3ES — HCSOTexas (@HCSOTexas) January 6, 2019

a man in the passenger seat opened fire, according to the affidavit. Gonzalez declined to name the second person, citing the pending investigation, but prosecutors identified Larry Woodruffe as the second suspect in a court hearing for Black on Saturday morning, Black confessed to homicide investigators that he drove the vehicle used in the shooting whilea man in the passenger seat opened fire, according to the affidavit. Gonzalez declined to name the second person, citing the pending investigation, but prosecutors identified Larry Woodruffe as the second suspect in a court hearing for Black on Saturday morning, the Houston Chronicle reported

Jail records indicate that Woodruffe is currently in custody on drug possession charges. He has not been charged in connection with the shooting.

Regardless of the suspect's race, "the family was surprised and relieved by the arrest," Merritt said.

"They wanted the right person to be convicted -- not a white person," Merritt said.