The Fort Worth, Texas, police officer who fatally shot a woman babysitting her nephew over the weekend has been charged with murder.

Aaron Dean was booked into the Tarrant County Corrections Center and later released on a $200,000 bond, according to jail officials.

Fort Worth police Sgt. Chris Daniels acknowledged the outrage that the killing of Atatiana Jefferson, 28, has sparked.

"To the citizens and residents of our city, we feel and understand your anger and your disappointment, and we stand by you as we work together to make Fort Worth a better place for us all,” he said.

Former Fort Worth officer Aaron Dean. Tarrant County Jail

The arrest came just hours after Dean's resignation from the police force. Interim police Chief Ed Kraus said during a press conference earlier that he intended to end Officer Aaron Dean's employment, but that Dean tendered his resignation first.

Dean, who joined the department in April 2018, still faces possible civil rights violations, Kraus said.

"Had the officer not resigned, I would have fired him for violations for several policies, including our use of force policy, our de-escalation policy and unprofessional conduct," Kraus added.

Dean was initially placed on administrative leave after he shot Jefferson to death. He has not been cooperating with investigators in the case, Kraus said.

It wasn't clear if Dean has a lawyer. The Fort Worth Police Officers Association did not immediately respond to a request for a comment.

A lawyer for Jefferson's family, Lee Merritt, said her relatives were "relieved" over the arrest.

"We need to see this through to a vigorous prosecution & appropriate sentencing," he tweeted. "The City of Fort Worth has much work to do to reform a brutal culture of policing."

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In a separate news conference earlier Monday, Jefferson's family demanded an outside investigation into her death.

"This man murdered someone," Darius Carr, Jefferson's brother, told reporters.

Kraus brought the case to the Texas Rangers, who he said were not inclined to take it up at that point, and to the FBI, which did not immediately say whether it would review it.

Fort Worth Mayor Betsy Price said she was "heartbroken" by the killing and said she asked City Manager David Cooke to hire a third-party panel of national experts to review the city's police department — "everything from top to bottom."

"This is a pivotal moment in our city, and we will act swiftly with transparency," she wrote in an open letter to the community.

Jefferson was playing video games with her nephew early Saturday morning when a neighbor noticed the front door of the house ajar. Concerned, the neighbor called the Fort Worth police department's nonemergency line to request a wellness check.

Body camera shows that when police arrived, an officer shined a flashlight through Jefferson's window and yelled, "Put your hands up — show me your hands," before firing a single shot at Jefferson seconds later.

Merritt called the Fort Worth police department's response to the situation "absurd" and said he was asking the U.S. Department of Justice to "come in and take a conscious look at the policies and procedures that allow something like this to happen."

The response to the wellness check by Fort Worth police, Merritt added, was "the equivalent of SWAT" — involving several officers "prowling" around the property before opening fire without ever identifying themselves as police.

The killing comes less than two weeks after Amber Guyger, a former police officer in nearby Dallas, was convicted of murder for fatally shooting a man in his home that she mistook for her own last year. In both instances, the officer is white and the victim was black.

Jefferson was staying at her mother's house in Fort Worth to help her recover from an injury when the shooting happened at about 2:25 a.m. Saturday.

Merritt said she had been playing video games with her 8-year-old nephew and lost track of time. Earlier that night, he said, the family had opened the front door to allow crisp fall air inside to cool down the house.

Fort Worth police have said they found a firearm inside the house, although it wasn't clear whether Jefferson was near the gun when she was shot. Merritt said it was legally owned and she had a license to carry.

The Fort Worth Police Department quickly released bodycam footage from the shooting. The video did not include the interior of the house, except to show a blurry image of the gun officers found after the shooting. Lt. Brandon O'Neil declined to answer questions about why police released the images of the gun; in her open letter Monday, Price called the gun "irrelevant."

Jefferson's family described her as an ambitious and kind person, with a college degree in biology who wanted to further her education.

Jefferson was "simply going on along with her life, living a law-abiding citizen's peaceful life, and she was killed by a reckless act of a Fort Worth police officer," an older sister, Ashley Carr, said. "There is simply no justification for his actions."

The Fort-Worth Police Department has come under scrutiny in the past. This year alone, there have been at least four other fatal police shootings involving officers; in three of those cases, police said the suspect was armed, but in the fourth, it was later discovered the man who was shot was holding a flashlight, not a weapon.

"I want to go ahead and dispel the myth that this is somehow a one-off, that this is just a bad luck incident from an otherwise sound department."

"I want to go ahead and dispel the myth that this is somehow a one-off, that this is just a bad luck incident from an otherwise sound department," Merritt said. "Fort Worth is one of the deadliest police departments in the United States. They are in need of serious systematic reform."

Jefferson's death prompted outrage in Fort Worth and across social media.

"This life mattered. This family matters. And we're demanding justice," Cory Hughes, a local activist, said Monday.

Amber Carr, Jefferson's sister and the mother of the boy who Jefferson was with when she was killed, said her son was helping her to stay strong.

"He's my motivation. He's my biggest encourager. In the middle of the night, when I'm crying, he tells me to breathe through my nose and out my mouth," she said. "He holds me, he hugs me."

In her letter, Price apologized on behalf of the city to Jefferson's family, and said, "To Atatiana's nephew, who has witnessed an unspeakable loss — sorry doesn't really cut it. This entire city needs to surround him with prayers, support and anything his family needs."