Boy 'shielded' sister from NSW killer dad

The teenage son of John Edwards, the 68-year-old Sydney man who shot and killed his two children last week, may have died while trying to protect his younger sister from their homicidal father.

Early ballistics reports show Jack Edwards, 15, may have been killed while "shielding" his 13-year-old sister, Jennifer, homicide squad commander Scott Cook said.

"That's a heroic act," he told reporters in Sydney on Thursday.

Det Supt Cook added the tests were inconclusive pending the final results of crime-scene tests.

"I have no doubt the coroner will seek to run an inquest in that matter," he said.