DALLAS — A murder warrant for Aaron Dean, the Fort Worth officer who killed Atatiana Jefferson, tells what led up to the shooting from the perspective of her 8-year-old nephew, who was in the room with her when she was shot.

The boy told a forensic interviewer that he and his aunt were playing video games together about 2:30 a.m. Saturday when she heard noises outside. She took her handgun from her purse and pointed it “toward the window” before she was shot, the nephew said, according to the arrest-warrant affidavit.

The 8-year-old saw his aunt fall to the ground. Jefferson, 28, was pronounced dead at 3:05 a.m.

Interim Police Chief Ed Kraus said at a news conference Tuesday that it “makes sense that she would have a gun if she felt that she was being threatened or there was someone in the backyard.”

That sentiment was echoed by an attorney for Jefferson’s family. Lee Merritt said Jefferson had every right to defend herself. The officers did not announce themselves as law enforcement.

“It’s only appropriate that Ms. Jefferson would have a gun,” he said at a news conference Tuesday, noting that the gun was legally owned and she had a license to carry it.

Merritt accused the Fort Worth Police Department of providing a defense for Dean by writing that Jefferson had pointed a gun at the window before Dean fired.

Fort Worth Mayor Betsy Price, speaking at a news conference a day earlier, said the gun was irrelevant.

“She was in her own home,” the mayor said of Jefferson. “She was taken from her family in circumstances that are truly unthinkable.”

Kraus said previously that the department’s decision to release a still image of the firearm found in the room where Jefferson was shot — without any further information about the weapon or what it had to do with the case — wasn’t the right call.

Dean, 34, was arrested at his attorney’s office about 6 p.m. Monday on a murder charge. He was freed from the Tarrant County Jail after posting $200,000 bond shortly after 9 p.m., court records show.

Kraus, who spoke before the affidavit was released, said it’s still unclear what Dean was thinking when he shot through a bedroom window, striking Jefferson.

The former officer, who resigned Monday, has not provided a written statement nor answered any questions, the chief said. Kraus had been prepared to fire the officer Monday morning, but Dean quit before he could.

Dean and another officer had been called about 2:30 a.m. Saturday to Jefferson’s mother’s home. A neighbor had called a non-emergency line to report that the home’s lights were on and its doors open.

An arrest warrant affidavit for Dean released by police Tuesday said the glass storm doors to the house were closed, but the front and side interior doors were open. Officers peered into the residence through the storm doors but did not see anyone, and they did not announce their presence, according to the affidavit.

In bodycam footage of the shooting, Dean walks around in the backyard of the home. About a minute and a half into the recording released by Fort worth police, Dean swivels toward a window, shouts at Jefferson to put up her hands and shoots her, all in a matter of seconds.

The chief said the shooting has been trying for the department.

Kraus got choked up as he likened the aftermath of the shooting to ants working to build an anthill, when “somebody comes with a hose and washes it away and they just have to start from scratch.”

“We have a great many officers who work extremely hard every day,” Kraus said. “I ask you please do not let the actions of one officer reflect on the other 1,700. There’s absolutely no excuse for this incident.”