When parts for high-powered assault weapons- the same semi-automatic assault rifles used in the massacre in Christchurch and the recent mass shooting in El Paso, Texas - started arriving in Sydney, law enforcement grew concerned about a local attacker.

What an investigation between the Australian Federal Police and the Australian Border Force actually found was Paul Gruber, a 44-year-old married disability pensioner from Berowra.

A Bush Master AR15 assault rifle, one similar to that used in recent mass killings in the USA. Credit:Joshua Lott

There is no suggestion that Mr Gruber is a white supremacist or planning a mass shooting.

Mr Gruber was arrested at Kingsford Smith Airport on Friday afternoon upon returning from China, where he was charged with three counts of importing Tier 2 goods without authorisation and one count of possessing more than three unregistered firearms without a licence.