A 17-year-old mother, her baby, and 5 other members of the family have died from the shooting
Video footage from a neighbor's security camera shows a toddler wandering outside his father's apartment brandishing a pistol.
School officials searched the child's backpack the day he shot his teacher, but did not find the gun.
The injury to the teacher was considered life-threatening, though she had shown some improvement in the hospital.
Investigators discovered that the seller had refused to sell the air rifle to the young man because he was Arab.
Gun crime is relatively rare in Australia, which implemented some of the world's toughest gun laws after a gunman killed 35 people in April 1996 at a cafe and tourist site in Tasmania.
Prosecutors allege that many of the suspects were members of the "Reichsbuerger" (Citizens of the Reich) movement, which does not believe in the existence of the modern German state.
The boy is being charged as an adult for first-degree reckless homicide and is being held on $50,000 bail. If convicted, he could face up to 60 years in prison.
The war has already seen heavy use of decades-old machinery and schematics. But what about century-old equipment?
The gunman did not hold back on criticizing those he worked with.