Update: Austin police have since identified the woman as Leslie Yolanda Salazar.
She weighed less than a 100 pounds, according to her father.
Austin police still have not yet released body cam footage, but say Salazar was intoxicated and "appeared to be in possession of a knife."
"We don’t know what led up to the incident that occurred here," Austin Police Chief Brian Manley said during a press conference, which can be seen above.
"She was described as being intoxicated. We believe that she assaulted some of the individuals that were in the home based on what we know right now," he said, adding the woman continued walking towards the officer instead of dropping the knife as she was ordered.
"And what’s evident on the body cameras, she does appear to be in possession of a knife, and the officers, again, gave her direction to drop that, but instead she continued in their direction," the chief explained.
Police say they were called to the scene in southwest Austin after a woman reported to a dispatcher a woman as trying to enter her home when her phone disconnected.
A few minutes later, the same woman called 911 again to say the woman was outside of her home, armed with a knife and seemed to be intoxicated and resisted efforts by others to be restrained.
After arriving, police say an officer ordered a Hispanic teenager to drop a knife, but she did not comply with his orders.
The officer, who has only been a cop for about two years, then shot the teenager.
She was pronounced dead at the scene.
"At the end of the day, this appears to be an 18-year-old female who lost her life today, and that is a tragic incident for this community and a tragic incident for our department," Manley said.
"This is not a situation that any officer wants to find themselves in."
Neighbors who witnessed the incident expressed concern about why deadly forced was used.
"I really think they use their weapons too fast before they try to deal in a different way," Flor Mojica, a neighbor in the area, told the Austin-American Statesman.
"If we can figure out another way to defend against a knife attack other than using a lethal weapon..." Daniel Hawkins said.
The shooting comes after Chief Manley directed changes regarding when his officers should resort to lethal means of force against suspects "only as a last resort" when other means have been exhausted.
Former APD officer Geoffrey Freeman was fired after she shot 17-year-old David Joseph who was naked running in the street when Freeman opened fire on him.
Freeman was eventually fired after body camera footage of the incident was released.
In that case, the City of Austin settled for $3.25 million in order to end the litigation process — the largest settlement in the city's history.
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