Tarrant County Sheriffs Office(FORT WORTH, Texas) — An 8-year-old boy who witnessed his aunt being fatally shot by a Fort Worth, Texas, police officer who fired through a window of their house told investigators she had retrieved a handgun from her purse and pointed it toward a window when she was killed, according to an arrest warrant issued for the officer. But police officials said 28-year-old Atatiana “Tay” Jefferson, the victim of the shooting early Saturday, was within her rights to protect herself and her nephew when she heard noises in her backyard and went to the window to investigate. The arrest warrant for now-former Fort Worth officer Aaron Dean, 34, was released on Tuesday, a day after he abruptly resigned from the police force and was charged with murder, stemming from the shooting of Jefferson. Fort Worth Police Chief Ed Kraus said Dean quit the force before he had a chance to fire him.“I realize that no action we take can replace the loss suffered here. I’m deeply sorry for what occurred,” Kraus said during a news conference on Tuesday to announce Dean’s arrest. “Human life is a precious thing, and should not have been taken from Ms. Jefferson. This incident has eroded the trust that we have built with our community and we must now work even harder to ensure that trust is restored.”The arrest warrant affidavit states that Dean and his partner arrived at Jefferson’s home about 2:30 a.m. on Saturday and never knocked on the door or identified themselves as police as they entered the backyard of the home and Dean opened fire almost as soon as he saw Jefferson standing at the bedroom window peering out.After being shot, Jefferson “yelled out in pain, and fell to the ground,” according to the affidavit.A neighbor had earlier called the police department’s non-emergency line to ask that a welfare check be conducted on Jefferson’s home because he noticed the front door was wide open, the neighbor, James Smith, told ABC affiliate station WFAA-TV in Dallas.“I called my police department for a welfare check,” Smith told WFAA. “No domestic violence, no arguing, nothing that they should have been concerned about as far as them coming with guns drawn to my neighbor’s house.”But on Tuesday, Chief Kraus told reporters that the officers believed they were responding to an “open structure” call, which would have required them to take more tactical precautions, including parking around the corner from the house.“The information came from the neighbor to the call takers and then while it was relayed to the dispatch it was determined to be an open structure call,” Kraus said in response to a question from ABC News. “I can’t tell you specifically if it was the dispatcher, but that’s something we’re looking into.”In the arrest warrant affidavit, Jefferson’s young nephew, Zion, told investigators that he and his aunt, who had a permit to carry a concealed weapon, were playing a video game in a back bedroom of their home when they heard noises outside.“She took her handgun from her purse,” the affidavit reads. “(The nephew) said Jefferson raised her handgun, pointed toward the window, then Jefferson was shot and fell to the ground.”Body camera footage released by the police department shows Dean approaching a rear window of the home with his gun drawn. The officer sees the woman through the window, shouts, “Put your hands up, show me your hands,” and fires one shot. Kraus confirmed that Dean never identified himself as police.“Perceiving a threat, the officer drew his duty weapon and fired one shot striking the person inside the residence,” a statement from the police department reads.Dean’s partner, identified in the warrant as L. Darch, told investigators she never saw Jefferson raise the gun before Dean opened fire.“Officer Darch said that they went into the backyard and Officer Dean was standing between her and the house and she could only see Jefferson’s face through the window when Officer Dean discharged his weapon one time,” the arrest warrant affidavit reads.Dean was arrested by a team of Fort Worth police officers on Monday evening at his lawyer’s office, Kraus said. He was booked at the Tarrant County Jail and released on $200,000 bond late Monday night.Efforts by ABC News to reach Dean and his attorney for comment have not been successful.The shooting immediately sparked outrage and protests from community members and Jefferson’s family.Fort Worth Mayor Betsy Price issued a public apology on Monday, saying, “there is nothing that could justify what happened on Saturday morning. Nothing.”While Jefferson’s relatives expressed relief that Dean had been arrested and charged with murder, an attorney for the family said Tuesday, “That’s not enough.”“We need more than a single arrest. We need appropriate prosecution, an effective verdict and proper sentencing,” said attorney Lee Merritt, who is representing Jefferson’s family in pending civil litigation.”Merritt said others in the police department need to be held accountable.“We need to go further up the stream. It’s time that we stop pulling babies out of the river and go further up the stream to see who’s putting them in there in the first place,” Merritt said referring to department policies and protocols that failed to stop Dean from using ill-advised lethal force.Calling the circumstances a “pivotal moment for the city,” Price said she had ordered the creation of a “third-party panel of national experts to review this department’s policies and procedures.Fort Worth City Manager David Cooke announced he will assemble an independent review board for the police department and will begin interviewing candidates for an independent police monitor.Chief Kraus became overcome with emotion on Tuesday as he described the toll the shooting has taken on the morale of police officers.“The officers are hurting,” said Kraus, appearing to tear up. “I’ve been out there on patrol and since this occurred … the officers they come up and hug. It’s very emotional because the officers try hard every day to try to make this city better.”“They’re out there trying to build these relationships and I likened it to a bunch of ants building an anthill and then somebody comes along with a hose and washes it away and they just have to start from scratch,” he said.He pleaded with citizens of Fort Worth to “please do not let the actions of one officer reflect on the other 1,700.”“There are absolutely no excuses for the incident and the person responsible will be held accountable,” he said. “Ms. Jefferson’s family and our community will have the last word and the courts will speak on her behalf.” Copyright © 2019, ABC Audio. All rights reserved.