Karen Stroebel thought her partner had found the perfect pet for their Western Australian hobby farm — a tall, dark and handsome alpaca named Harry.

But beneath his furry exterior, Harry was concealing a near-uncontrollable rage.

He had only been living at his new home in Mount Barker for just over a week when he snapped, trampling Karen into the ground and almost causing her mother to suffer a heart attack.

The women feared for their lives, and it was only the quick actions of a neighbour and two local policeman that saved them from the aggressive animal.

Dirty Harry

Karen Stroebel's partner acquired the alpaca from a workmate and brought him home to their small property.

Harry the angry alpaca, pictured before his attack. ( Supplied )

The animal showed his true colours almost immediately, attacking Ms Stroebel on the day of his arrival.

"Because he looked so beautiful, we thought that spitting at us was part of his love for us," Ms Stroebel said.

"After I had welcomed him from the horse float, he was in the paddock and I was just leaving to walk to the gate.

"He came up behind me and bit me on the back.

"Luckily I had a loose shirt on and he just grabbed my shirt."

Ms Stroebel turned towards the animal who then bit her a second time on the arm, causing her to fall.

"At that time my partner had a beer in his hand and was beating him over the head with the beer bottle and I was able to get up," she said.

A sign of things to come

Ten days later, Ms Stroebel's 78-year-old mother, Pat, was visiting the property and the two women were working in the garden.

Harry was 20 metres away in the paddock when he suddenly reared up and jumped over the fence.

Ms Stroebel tried to guide him back towards the gate when things escalated.

"As soon as he got to the gate, he just reared up and smashed me into the ground very violently," Ms Stroebel said.

"He bit me on both my arms and after I instinctively turned over, he bit me on the back of the neck and started to trample me.

"He trampled my shoulder with his hoof and at this point my mum was beating him with a broom.

"She got him away and told me to run."

The two women managed to get away from the angry alpaca momentarily, but then he bailed them up in a corner against the house.

Sergeant Seton at the spot where Harry trampled Karen Stroebel into the ground. ( ABC Great Southern: Ellie Honeybone )

Alpaca warfare

Harry had the humans trapped and continued to rage and rear.

Terrified and running on adrenalin, Ms Stroebel and her mother began trying to beat him away with a broom and rake.

"We really started hitting him and pushing him back. He would retreat again for a while but then come at us again," she said.

"This went on for about an hour and a half, and at this stage he was bleeding out of his nose.

"I said to mum 'oh no, poor Harry' and I was really concerned that Harry was bleeding out of his nose.

"Mum was sort of looking at me like 'stuff poor Harry, we're just about to get killed here'."

Harry bailed the two Stroebel women up under this verandah. ( ABC Great Southern: Ellie Honeybone )

For a time, Ms Stroebel hoped Harry would let up and back away.

"But then it was just clearly warfare," she said.

"He was spitting blood and everything at us and rearing up at the same time.

"His eyes looked totally demented, like his eyes were totally mad."

A last resort

Pat Stroebel lives with a heart condition, so when her face began to lose its colour Ms Stroebel knew they were in mortal danger.

"She just went pale, leant forward, dropped the shovel and fell, and that's when I started screaming hysterically because I was just so worried that mum was going to die," Ms Stroebel said.

"So we just screamed and screamed and screamed."

Luckily those screams were heard by a concerned neighbour on the other side of a major highway who called the police.

Sergeant Seton and Pat Stroebel at the farm in Mount Barker. ( ABC Great Southern: Ellie Honeybone )

Sergeant Laurie Seton was one of two officers who attended the scene.

"As we drove past the house I looked out and could see this large alpaca and two ladies holding shovels above their heads," Sergeant Seton said.

"I thought 'you don't see that every day.'

"As I jumped out of the car and came around the verandah, the alpaca turned his attention off the ladies and came straight at me."

Sergeant Seton said while he had not dealt with many alpacas before, Harry was certainly one of the biggest he had ever seen.

The policemen eventually managed to frogmarch the alpaca back into the paddock, much to the relief of the Stroebel ladies.

Long-term injuries

It was October 22 when Harry attacked, but Karen Stroebel is only due to leave hospital this week.

She suffered damage to the nerves in her spine and bulged discs from when the alpaca first threw her 1.57-metre frame to the ground, and remains under heavy medication while she heals.

Her mother, Pat, suffered a gash to the head but has made a full recovery, with her heart rate back under control.

Harry returned to the farm where he came from but continued to display aggressive behaviour, attacking other alpacas.

In the end, the decision was made to euthanase him.

"We believe he was just a rogue alpaca," Ms Stroebel said.

"We wouldn't have survived without the police — we wouldn't have been able to keep fighting."

Alpacas are usually considered gentle creatures. ( ABC News: Rebecca Carmody )

Entire males not the best pet option

Mahlon Hotker runs an alpaca stud in Albany and has been working with the breed for 16 years.

He said while they were normally fairly gentle animals, aggression was not unheard of.

"You hear of the odd occasion but it's very rare and in all instances, it's been an entire [not castrated] male," he said.

"Herd males need to be aggressive and entire males are definitely not for pets."

Harry the handsome alpaca was an entire male, and Pat Stroebel acknowledged that he was not the right fit for the small hobby farm.

"Not all animals are like this, but if there is a rogue then it's dangerous," she said.

"I think it's important that people know the animal [they are caring for] and that it has been castrated and that it's friendly."