Twenty never-registered guns were found late last week stuffed inside unlocked cupboards or barely concealed underneath beds. 

Among the haul were four self-loading rifles, two pump-action shotguns, a self-loading  and one shortened firearm. Police also found several thousand rounds of ammunition inside the home.

Such rapid-fire weapons have long been prohibited in Australia under legislation introduced in the wake of the Port Arthur massacre.

‘‘These guns here are the upper level – they don’t come any more serious than this,’’ Lake Illawarra police Licensing Sergeant Gary Keevers said. 

The man was 88 when he died. 

Police say he lived alone in a typical suburban street and was once a recreational hunter with six registered firearms to his name. 

But police seized those guns in 2011 after the man disclosed a mental illness, in line with requirements of the Firearms Act.

The inside of the man’s house was crowded with his personal possessions and rain water had been allowed to leak in through the roof, wetting some of the guns and forming mildew in parts.

Police searched the property on Thursday after the man’s daughter found a single firearm and phoned Lake Illawarra Local Area Command. 

‘‘By the time we got there she was up to 10,’’ Sergeant Keevers said.  ‘‘His family members are so shocked to know of the firearms secreted in the house.

‘‘I’ve been doing licensing for 14 years. I’ve never ever seen 20 [never-registered] firearms...come out of a residential premises.  His [motives] are going to remain a mystery because he’s passed away.’’

The cache has intrigued police partly because the man had no criminal history.

Also, his selection was wide and varied – seemingly at odds with a collector’s ways.

The prohibited weapons included a shortened firearm, a military-style SKS self-loading rifle, a MI30-calibre Carbine self-loading military rifle and a fully-loaded LR.22-calibre Ruger self-loading rifle.

Possession of prohibited firearms carries a maximum 14-year jail penalty.

Lake Illawarra licensing police released details of the seizures on Tuesday to encourage the continued surrender of prohibited firearms.

Gun owners should surrender the weapons to police even outside of an official amnesty, Sergeant Keevers said. 

‘‘They will not be prosecuted, he said. 

Almost 20 years on from the Port Arthur massacre, there are as many guns in Australia now as before John Howard’s buy-back scheme destroyed more than 631,000 firearms.

And Mr Howard warns it’s a mistake to believe guns like that used by Martin Bryant in Tasmania in 1996 are not making their way to Australia.

Bryant, a man with a history of violent and erratic behaviour, killed 35 people at Port Arthur when he opened fire with an automatic rifle similar to that used at Sandy Hook elementary school in Colorado in 2012, when 20 children and six teachers were fatally shot.

‘‘I would never be so foolish as to say that guns like that can’t get into Australia,’’ the former prime minister said.

‘‘The evidence is that, to date, close to 20 years after the tragedy (Port Arthur), that we have learnt something from it.

‘‘That doesn’t mean to say that you shouldn’t be revising and keeping it up to speed, and you shouldn’t be complacent.’’

The Port Arthur massacre transformed gun control legislation in Australia.

‘‘Like everybody else, I was just stunned,’’ Mr Howard told a gathering at Kirribilli House on Tuesday hosted by Gun Control Australia, speaking of the events of April 28, 1996.

‘‘My reaction was astonishment and I pretty quickly felt that I had to do something. This terrible lunatic had gone on this murderous rampage and all these innocent people had been killed.’’

The gun buy-back introduced by Mr Howard purchased and destroyed more than 631,000 firearms.

But controls over firearms have since been slowly wound back.

The number of firearms held by civilians in Australia has reached more than three million; four states have eliminated the 28-day cooling off period when applying for a second weapon; and one licence-holder in NSW has been allowed to acquire 329 guns and another in Victoria has been granted permission to have 131 firearms.

Port Arthur survivor Carol Loughton was in Sydney to join calls for more action to ensure there is not another such tragedy.

She was in the Broad Arrow Cafe with her daughter Sarah when Bryant started shooting.

‘‘She (Sarah) was shot in the back of the head and I threw myself over her, trying to save her,’’ Ms Loughton said.

Carol was shot in the back.

Ms Loughton said there are still 18 people living with extremely severe wounds.

‘‘I’m seeing a surgeon again later this month. I’ve had more than 30 operations,’’ she said.   AAP