A former prison guard who amassed more than 200 deadly weapons has been taken to a mental health institution.

Michael Kay, who worked in Sydney prisons for 30 years, was banned from owning a gun nine years ago due to poor mental health but managed to accumulate 213 weapons, the Daily Telegraph reported

The cache of weapons included semiautomatic guns, knives, swords and 2000 rounds of ammunition.

Stuart Smith, NSW Police's Acting Commander of the State Crime Command, said Mr Kay had spent three days in the mental health institution after developing 'quite acute behaviour' in custody.

Mr Kay (pictured), who worked in Sydney prisons for 30 years, was responsible for breaking up jail riots and extreme violence as a member of the prison tactical Immediate Action Team

The former 'high-risk' prison guard who amassed more than 200 weapons has been taken to a mental health institution

A routine firearms prohibition order search brought police officers to the 64-year-old's home in Richmond, Sydney's north west

Mr Kay was arrested by officers while taking the garbage out at his north west Sydney home and officers found five knives on him.

A routine firearms prohibition order search brought police officers to the 64-year-old's home in Richmond on Tuesday.

They were not expecting, however, to find the military-grade arsenal hidden away in his shed on Tuesday.

Officers seized several military-grade rifles including an SKS automatic, a .357 Magnum revolver, a 9mm Luger and thousands of rounds of ammunition.

They also found three crossbows with more than 100 arrows, knives, tomahawks and swords.

Mr Kay collected a substantial amount of telling literature related to sniper training, military tactics and counter-terrorism operations.

Police have seized more than 200 weapons (pictured) from Michael Kay, a 'high-risk' former prison guard

Mr Kay also owned clothing with anti-Islamic sentiments and 'doomsday' patches embroidered

A State Intelligence Command profile of the former prison guard revealed he suffered from a history of mental health issues and an obsession with weapons

Mr Kay was responsible for breaking up jail riots and extreme violence as a member of the prison tactical Immediate Action Team before being dismissed in 2010.

A State Intelligence Command profile of the former prison guard revealed he suffered from a history of mental health issues and an obsession with weapons.

He also owned clothing with anti-Islamic sentiments and 'doomsday' patches embroidered.

Commander Smith said: 'We can only interpret the evidence from the scene, and (he was) obviously a deeply disturbed individual who was highly trained with military grade weaponry.'

This was coupled with extensive ballistic protection and reading materials.

'The threat was real, it was significant, and it was imminent.'

Commander Smith said NSW Police will continue to remain vigilant to mitigate future risk as they 'are conscious of what is happening around the world.'

Officers from the Drugs and Firearms squad said the alarming finding was unlike any other case and there were concerns he could have been planning a mass shooting

Officers found three crossbows with more than 100 arrows, knives, tomahawks and swords

Officers from the Drugs and Firearms squad said the alarming finding was unlike any other case and there were concerns he could have been planning a mass shooting.

State Crime Commander Acting Assistant Commissioner Stuart Smith said the findings posed a significant threat to the community.

'What we found at the premises was a disturbing individual who had a cache of tactical weapons and 50 times the ammunition required of a sports shooter, and concerning literature,' he said.

'As we were itemising the exhibits, we realised the potential of what was in that yard.'

State Crime Commander Acting Assistant Commissioner Stuart Smith said the find (pictured) posed a significant threat to the community

Police were tipped off by Australian Border Force officers two weeks ago when Mr Kay made numerous online transactions in a short period, including gun parts and bulletproof clothing (pictured is seized ammunition)

Det Supt Smith said: 'He amassed such a huge cache of weapons you can only interpret what you find and be concerned by that' (pictured is a seized crossbow)

Mr Kay has faced court twice for charges related to firearms since his license was revoked in 2009 but was not penalised due to mental health (pictured are some of the seized weapons)

Police were tipped off by Australian Border Force officers two weeks ago when Mr Kay made numerous online transactions in a short period, including gun parts and bulletproof clothing.

Mr Kay has faced court twice for charges related to firearms since his license was revoked in 2009 but was not penalised due to mental health.

Mr Kay was arrested and taken to Windsor Police Station before being admitted into a mental health instituion.

Police expect to charge him with at least 20 charges when he is released.

Officers seized several military-grade rifles including an SKS automatic, a .357 Magnum revolver, a 9mm Luger and thousands of rounds of ammunition (pictured, left, right, are two of the guns seized)

Mr Kay was arrested and taken to Windsor Police Station before being admitted into hospital due to mental health (pictured is seize ammunition