Updated at 6 p.m. Aug. 2: Revised to include the officer's body-cam footage.

ARLINGTON — An Arlington police officer took just seconds to fire three shots — one of which fatally struck a woman — after a dog started running toward him Thursday afternoon, body-camera footage shows.

Maggie Brooks (via Facebook)

Authorities had been called to perform a welfare check on 30-year-old Margarita "Maggie" Victoria Brooks, who was reported to be passed out in a grassy area near a shopping center she frequented.

Brooks, the daughter of an Arlington fire captain, was struck once in the chest and died at 6 p.m. at Medical City Arlington Hospital, according to the Tarrant County medical examiner's office.

The dog survived and was taken to an animal shelter. It was unclear whether it was Brooks' dog.

Authorities were called about 5:15 p.m. to check on Brooks, who was lying in a grassy area near Cantor Drive and North Collins Street.

As a police officer approached her, an unrestrained dog began to run at him and bark, police said. The officer retreated from the dog, pulled out his gun and fired three times.

Police said that Brooks yelled after the shots were fired and that it was "apparent she was injured."

According to Police Chief Will Johnson, the officer had undergone eight hours of training for canine encounters, as well as mandatory firearms training.

"Everything about this call is an absolute tragedy," Johnson said at a news conference Friday afternoon. "Our hearts are broken for the Brooks family and the police officer involved."

The dog, which officials think was grazed by a bullet, is in quarantine at the Arlington animal shelter, police said. Officials described the dog as a 40-pound Labrador retriever mix.

The officer, whose name has not been released, is 25 and has been with the department seven years, police said. He started as a detention officer, graduated from the police academy in February and was cleared for field work July 1, police said.

He was placed on administrative leave, which is routine in shootings involving police.

Authorities are conducting a criminal investigation, which will be handed off to the Tarrant County district attorney's office, as well as an administrative investigation to determine whether the officer failed to follow department policy.

The shooting was recorded on the officer's body camera, which Brooks' family was shown Friday afternoon. The department released the footage publicly later in the day.

Warning: The following video contains graphic content.

In the footage, the officer is heard asking, "Hello? Are you OK? Is that your dog?" as he walks down a sidewalk behind the shopping center.

"Can you get —" he says as the dog starts running toward him and barking. "Get back!"

Two seconds later, the officer fires three shots toward the dog while backpedaling. The dog turns away and runs back toward Brooks.

"What the [expletive]," Brooks screams. "Oh my God. Police shot me."

The officer reports that three shots have been fired and then approaches Brooks, telling her, "Ma'am, get a hold of your dog" as the footage ends.

Larry Hamilton, a 64-year-old who often tries to find work outside this Arlington Walmart, said he knew the woman killed by an officer as well as her boyfriend. He said they had a small brown dog and “she was real loving to the dog.” The dog “was her soul,” he said. pic.twitter.com/2wCLbGocxb — Jack Howland (@JHowl04) August 2, 2019

Brooks, whom acquaintances described as homeless, had become a fixture at the shopping center, along with her boyfriend and dog, according to workers and residents.

The dog was well taken care of and routinely got fed "before she did," 64-year-old Larry Hamilton, who lives nearby and knew Brooks, told the Fort Worth Star-Telegram. He called the dog "her soul."

Justin Patton, who owns CBD American Shaman, said that everyone there knew Brooks and her boyfriend to be friendly and that they never caused problems. He said Brooks always appeared to be put together, but that she and the boyfriend were there every day.

Patton also said it was hard to believe her dog was being aggressive because it was always friendly.

A manager at a Subway that Brooks visited often said that the "down-on-their-luck" couple had been there for months and that her boyfriend often offered to wash customers' windows for tips.

Customers were leaving money throughout the day Friday to give to her boyfriend, according to the Subway manager, who declined to give her name.

One employee at a Walmart Neighborhood Market in the strip mall said Brooks and her boyfriend would rest under a large tree in the parking lot.