"APD is now on scene of an active shooting incident at Great Hills Trail and Rain Creek Parkway".
Police are still looking for the shooter, which they believe is Stephen Nicholas Broderick. On Sunday, police swarmed the area searching for 41-year-old Stephen Broderick, who is considered armed and unsafe.
The chief said that this shooting incident appears to be "domestic", and that the victims were known by the suspect.
Police know the identity of the gunman, according to a report by KVUE-TV in Austin.
Chacon said the danger remains high and authorities asked area residents to shelter in place as authorities search for the suspect.
Three dead in 'active attack' shooting incident in northwest Austin, medics say
She said they responded to an area that included a strip mall, several retail stores with a large apartment complex behind it. He said Broderick knew the victims but didn't elaborate on how or provide a motive for the shootings.
She said the first 911 call came in at 11:44 a.m. and that three adults were fatally shot.
The shooting was targeted and the three victims - two women and one man - knew Broderick, according to Chacon.
Residents were cautioned to avoid the area while those in the locality were requested to take shelter.
Sheriff's spokeswoman Kristen Dark tells the Austin American-Statesman that Broderick, a property crimes detective, resigned after the arrest. A child was involved but has been located and is safe, he added.
The newspaper also reports that Broderick's wife filed for a protective order and divorce shortly after his arrest. The area where officers responded includes a strip mall and several retail stores with a large apartment complex behind it.