When NSW Police received information a man was manufacturing explosives and guns at his property in Sydney's northwest, they knew they had to act swiftly.
About 11am on Wednesday police raided a Kurrajong property where they seized 39 guns, 77 knives, thousands of rounds of ammunition, silencers, improvised explosives and the chemicals to make more.
Detective Superintendent John Watson says the significant number of prohibited weapons at the property "can only be described as alarming" and a 42-year-old man has been charged.
It was apparent he had been amassing these things over a period of time, Mr Watson said.
But it's not clear yet exactly what for.
Watson says police don't believe an attack was imminent, they don't think his alleged manufacturing of the weapons or explosives was related to terrorism or extremism and he doesn't appear to have been working as part of a larger group.
"This person is working alone, living alone in a rural setting... he was manufacturing weapons himself at the property," Watson said on Thursday.
While it doesn't appear to have been preparation for an act of terrorism, "there is no doubt in our minds this matter posed significant risk to this individual, his family, but also the community at large", Watson said.
Police are still guarding the property as investigations continue.
As well as the 77 knives at the property, the man police arrested during a traffic stop in nearby Grose Vale has been charged with having one on him in public.
He has also been charged with offences including possessing unregistered firearms and prohibited weapons, as well as manufacturing firearms without a licence.
The man will face Penrith Local Court on Thursday.