Kellaway Crescent emergency services in Mill Park were called around 7.50 p.m. in response to reports of a stabbing.
It also announced the death of a 39-year-old woman at the scene.
Police said they found a man, a woman and a girl believed to be known to each other, with serious injuries.
The girl was taken to hospital in critical condition, where she died.
Police said the 40-year-old man, who is under police escort at the hospital, is also in critical condition.
Anyone with information should contact Crime Stoppers at 1800333000.