When a couple of 12-year-olds muck around on bushland at the edge of suburbia, it's usually harmless.

Unless, that is, they live near a defunct animal park, where the exotic and dangerous wildlife stayed long after ticket sales ended.

In the Warragamba area in Sydney's outer west there are the remains of the African Lion Safari—a tourist attraction that gave patrons the chance to have their car windows licked clean by lions.

Its television advertisement included the lyric, "It's scary, but nobody cares".

Ian Berry, a former local police sergeant, still remembers visiting the park with his family.

"It was an experience. We brought the kids out," he said.

"The lions would be wandering around, but you knew there was a minimum of two sets of security fencing to stop them going anywhere."

The African Lion Safari was run by the Bullen family, whose connection to animals ran three generations deep of circus and animal training.

After the attraction closed to the public in 1991, many animals remained living within the park's confines, under the supervision of the Bullen family.

A lion close up at the African Lion Safari. ( John Fuller )

The lion escapes

Late one night in August 1995, Ian Berry and Detective Sergeant Fran Ralph received a call to attend a "lion wandering the streets", the pair had an initial reaction of disbelief.

"I got the radio call, and I said: 'Is there a pink elephant with it?'" Mr Berry said.

They arrived at Marsh Road in Silverdale, convinced they had been called out for no reason.

"Then of course, this lion just slowly walked out in front of our police car. To be honest, I almost had a heart attack," Detective Sergeant Ralph remembered.

Mr Berry called for assistance: "Radio, can you get Brenton Bullen here ASAP."

Lions resting at the African Lion Safari in Warragamba, NSW. ( Supplied: Owen Gill )

On one of the houses in the street, a verandah light flicked on and off, rapidly.

Inside was Jaqueline Shalavin, who lived with her husband and three young children, trying to get the attention of the police outside.

"My dog screeched, yelped. I said to my husband, 'I think there must be a burglar in the yard,'" she said.

But a lioness had found its way into the Shalavins' backyard and their pet border collie, Boffin, was in the jaws of the big cat.

"I did find the dog," said Mr Berry.

"But I wasn't going to ask it to give it back."

Mr Bullen arrived at the Shalavins' home with a bag full of specialised equipment.

The second son of the well-known animal-keeping family talked options with Mr Berry.

"Sedate it or net it. I was happy with either of those options," Mr Berry said.

"But because of the lion's location, and the fact of hitting it with a tranquiliser and it going birko, it would have been pretty well dangerous for everyone."

Mr Bullen came to an unfortunate and last-resort decision, retrieving a high-powered rifle from his bag.

"He said, we'll have to take it out," Mr Berry remembered.

Detective Sergeant Ralph recalls Mr Bullen's emotional state just after the lioness was shot.

"He was distraught, just like we were. They loved those animals. It was emotional."

How the lion got away

A few weeks before the lioness escaped, Adam—not his real name—had been at the local bike jumps, playing with a friend.

They ran alongside a tall fence at the border of the old lion park. Adam and his young mate were primary schoolers at the time.

Local kids had seen non-threatening buffalo at the park's fence-line as a regular event.

"You could poke them with a stick," Adam recalled.

They were also accustomed to hearing lions being fed in distant cages as they sat down to their own family dinners. It was all part of living next to the old park.

Adam remembered it as being "cool".

The drain where the lions managed to escape. ( ABC RN: Timothy Nicastri )

That day, with the boredom of the local area at a peak, the two 12-year-olds climbed into a small stormwater pipe which crossed under the lion park fence, near the bike jumps.

At the end of the storm pipe was a metal grate. The boys began to kick it.

"It was probably about 30 kicks. We were determined," Adam said.

"When you've got a lion safari in your backyard you might as well go check it out."

Once the rusting grate broke away, the boys went into the park, explored a bit, fished for yabbies, and then retreated back to the suburban side of the storm pipe.

The thought of a lion escape never crossed their minds.

Adam's sense of responsibility for what took place in the Shalavin's backyard is limited. He considered his actions as simply part of the chaos of youth.

"Boys will be boys," he said.

"I don't feel any guilt, because I know all I did was be a 12-year-old kid.

"How the hell was I supposed to know that a lion would escape from its cage and use that as its exit point? It was just one leg in a series of events."

At the time, Stafford Bullen told news reporters that the lions "would have had to escape from their night house and go through two fences".

A lioness strolls around the grounds of the African Lion Safari. ( Supplied: Owen Gill )

The pregnant lioness

After the lioness was shot in the Shalavins' backyard, it was discovered she had been expecting a cub.

"She was beautiful. We carried her from the back yard to the front yard," Detective Sergeant Ralph said.

"It was extremely disappointing, and to this day for me it's extremely disappointing."

The information that the lioness was pregnant was changed Adam's perspective who's now a father of two daughters.

"It's bloody unfortunate it happened. With the lion being pregnant, it makes me feel remorse. It changes things," he said.

But Adam still occasionally tells this tale of unintended consequence from his boyhood, and laughter remains a part of it.

"It's just so farfetched," he said. "Bloody crazy."

Or, in the words of Mr Berry: "Funny, but not funny."

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