A man who allegedly stockpiled guns, more than 2000 rounds of ammunition, swords, knives and crossbows at a western Sydney home was an “imminent threat”, police say.

Detectives found the stash – along with ballistic vests and masks, armoured helmets and terrorism and emergency response books – while searching the Richmond home.

NSW Police arrested a 64-year-old man, who remains in hospital after being taken for a mental health assessment.

State Crime Command Acting Commander Stuart Smith said the man is a former prison officer, dismissed from Corrective Services NSW, with weapons training, ABC reported.

Police do not know what the man was planning to do with the weapons.

“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 and reading material … coupled with ballistic protection,” Mr Smith said.

“The threat was real, it was significant, and it was imminent.”

Police executed a search warrant last Tuesday after receiving a tipoff from Australian Border Force about imported firearm parts.

Officers seized five rifles, including a semi-automatic Norinco SKS, firearms parts and accessories, more than 2000 rounds of ammunition, three crossbows and more than 100 arrows.

There were more than 100 knives and swords, the ballistic vests and masks, armoured helmets, handcuffs, and the literature.

Police returned on Wednesday after being contacted about a suspicious bag hidden in a concrete stairwell at the back of the property.

Investigators returned to the home and found five further firearms, including pistols and handguns.

The firearms will undergo forensic and ballistic examination.

The 64-year-old is expected to be charged when he’s released from hospital.

Inquiries are continuing.

-with AAP