Twin brothers at the centre of Willunga shooting took the same powerful hallucinogen as Cy Walsh

Mark Mooney

The twin brothers at the centre of Friday's tragic fatal shooting south of Adelaide had experimented with the same drug as Cy Walsh used before he stabbed his father to death, Seven News can reveal.

Jake and Lucas Cawte document their South American spiritual journey.

The 24-year-old's weren't just twins – they were best mates.

But something set Lucas off Friday morning when he allegedly shot Jake in the head, killing him at the family home in Willunga before handing himself in.

Luke Cawte has been charged with murdering his twin brother. Source: 7 News
Jake Cawte was shot on the family property south of Adelaide. Source: 7 News

The men's distraught mother told 7 News that while in South America, they had experimented with the powerful hallucinogenic drug "ayahuasca".

It's the same drug Cy Walsh had taken in the years before killing his father.

After hearing about Phil Walsh's death in 2015, the Cawte family became worried about Lucas and Jake's state of mind.

The twins had gone on spiritual journey to South America together. Source: 7 News
They documented the journey and their experience taking the drug ayahuasca. Source: 7 News

They had returned from their trip different people.

"They have changed their outlook on life completely," forensic toxicologist Andrew Leibie said.

"They feel like they're a different person based on the things they've seen and perceived while they're taking this drug."

The hallucinogen was the same one Cy Walsh took in the years before he stabbed his father to death.
Tributes have been left for the family at the property in Willunga. Source: 7 News

Lucas has also been battling mental illness and had been in and out of the Margaret Tobin Centre at Flinders.

He is being held at the centre again following his arrest.

His mother says she is desperate to visit him and is vowing to "wrap her arms around him and stand by him… no matter what he's done."

Luke's mother said she will stand by her son. Source: 7 News

The men's mother hopes the tragedy will serve as a warning about the dangers of hallucinogenic substances.

It's understood the men's father keeps guns at the property but it's unclear if one of them was used to kill Jake.

If you are concerned about the mental health of yourself or a loved one, seek support and information by calling Lifeline 13 11 14, Mensline 1300 789 978, or Kids Helpline 1800 551 800