The brother of the perpetrator said his family "could not manage" of their child and he worried his younger sibling would fatally harm a person of their household, a public inquiry has been told.
The individual, then 17, fatally attacked three youngsters at a Taylor Swift-themed dance class on 29 July 2024.
The hearing, sitting at a civic building, learned the sibling the older brother warned a friend there was a possibility of his brother "taking action potentially fatal."
The hearing was told Dion messaged his friend over the online platform: "The fights are terrifying because of the risk of a fatality."
The sibling said his brother was similar to the psychopathic killer in the picture the thriller.
Growing Tensions
The inquiry was told he was identified with a neuromuscular disorder at the age of 12 which caused him needing mobility assistance and his mother and father offering greater support.
When asked by the inquiry counsel, attorney, if that altered their dynamic he replied: "There was tension that emerged."
Dion concurred his sibling seemed to dislike this change.
He testified the inquiry that after the family relocated from Cardiff to their new location his sibling's temperament declined and he would have "aggressive episodes."
The hearing heard Dion became "progressively concerned" of his sibling, who would strike him often.
He stated: "I needed to be careful if I did speak to him because any disagreement could become an altercation."
'Genuine concerns'
He testified his relative became increasingly physical after he was expelled from Range High School in Formby, Merseyside, in October 2019.
He departed for higher education in 2022 and the siblings communicated rarely "as he was unaccustomed to having me around."
Proceedings was informed of a communication Dion sent to a contact on Discord in which he stated his brother was angered by him talking during nighttime because of the poor insulation in their home.
He additionally informed his contact there was a danger of "him doing something potentially fatal."
He stated: "Arguments are frightening because of the threat of a fatality."
The lawyer inquired: "You were genuinely concerned that your brother would fatally harm a individual of your household?"
Dion replied: "In case matters intensified to that level."
The lawyer asked how his mother and father dealt with the perpetrator's aggression.
"There was no point to try and punish him," he said. "Moreover, there was a serious threat in taking that action.
"We said there was a overall danger to safety in casual discussion, if you seek to address him... it would not end well."
When Mr Boyle asked if his parents had lost control of his sibling, he acknowledged.
Questioned regarding his relative being similar to a persona from the film No Country for Old Men, Dion explained: "It was said that persona's meant to be a psychopath and that's why I used the word there."
The brother revealed the last interaction he had with his relative was in the 2023 summer.
He confirmed that their family requested the perpetrator to take leave to him as he was going to meet his friends and his relative tossed a container at him but the exit was secured before it made contact.
Proceedings proceeds.
