The sibling of Axel Rudakubana reckons the mass killer grew "increasingly withdrawn" following his exclusion from school for assaulting a fellow pupil.
The Southport attacker's elder brother Dion has spoken out publicly for the first time, recognising the "most immense pain, anguish and grief to the lives of so many people".
In a statement submitted to the ongoing Southport Inquiry through his top barrister, Dion Rudakubana called for the proceedings to examine "whether more could have been done" by public sector agencies to prevent the killings.
Jacqueline Carey KC, who will represent Mr Rudakubana's interests at the inquiry, said: "Dion wholeheartedly supports the inquiry's aim to identify lessons which will minimise the prospect of such harm being caused in the future."
READ MORE: Prisoner charged with murder after inmate found dead in cell at HMP Exeter
READ MORE: Death row inmate's chilling final words before execution for killing wife's family
Axel Rudakubana was merely 17 when he launched the mass stabbing assault at the Taylor Swift-themed class at the Hart Space in Southport on July 29 last year, reports the Liverpool Echo.
Armed with a blade purchased on Amazon and "specifically targeting women and girls", Rudakubana stormed in whilst the youngsters were crafting bracelets and commenced his rampage.
Rudakubana, who is only being identified during proceedings as AR, slaughtered Alice da Silva Aguiar, nine, Bebe King, six, and Elsie Dot Stancombe, seven, in the horrific incident.
He also severely wounded eight other children, who cannot be named for legal reasons, as well as teacher and party organiser Leanne Lucas and local businessman John Hayes. Legal representatives acting for the victims of the horrific attack have informed the inquiry that crucial warning signs spanning days, months and years were overlooked, with the perpetrator's history of disturbing and violent conduct left unaddressed.
In his written submission, Dion Rudakubana, who is designated as a core participant in the inquiry, stated "AR's expulsion from school in October 2019 and the reasons behind that exclusion plays an important part in AR becoming progressively more isolated from his friends and family".
The inquiry was told that in October 2019 Axel Rudakubana was studying at Range High School in Formby when he was kicked out after informing Childline he had repeatedly brought a knife into school and "viciously attacked" an alleged school bully. During police questioning about his readiness to use a knife, he responded he was "pretty certain".

After being thrown out, he was sent to a pupil referral unit, which repeatedly flagged him to the counter-terrorism scheme Prevent. Yet the system failed to identify how dangerous he was and, in subsequent years, he "dropped off the radar", barely ever venturing outside.
A spokesperson for the 18 families whose children attended the dance class but survived told the inquiry that Axel Rudakubana had "displayed a propensity for serious violence" across several years. The inquiry was told he had also shown a "willingness to carry and to use weapons".
The court heard that Rudakubana had a previous conviction for assaulting a child in December 2019, was found carrying a knife on a bus in March 2022 and had placed over a dozen orders for weapons including three machetes in the years leading up to the attack.
Dion Rudakubana, who was born two years before his brother while their family resided in Cardiff, is a wheelchair user and was studying at Warwick University at the time of the attack. It's understood by the ECHO that he was part of the university's brass band society.
His solicitor told the inquiry that "Dion was wholly unlike his brother - a thoughtful young man, of good character, studying at university". The statement on his behalf added: "As Dion explained in his police statement, he returned home from university the weekend before the attacks and in that statement, he sets out as best he could his knowledge of what AR was like that weekend and indeed what AR was like in the years preceding the incident.
"By virtue of his studies and his disability, Dion had limited interaction with his brother but Dion is aware that in addition to police involvement with AR, agencies such as social services and CAMHS were also involved with his brother."
The grieving families have questioned the responsibility of Axel Rudakubana's family, stating they "knew and ignored the risk he posed to the public".
The inquiry at Liverpool Town Hall has heard that a "significant" theme of the proceedings will be Rudakubana's relations with his family, particularly his behaviour in the week leading up to the attack and their knowledge of the weapon-obsessed teen's online purchases.
Questions are expected to be raised about Axel Rudakubana's access to weapons, some of which were hidden from him by his parents. The inquiry has also already heard how his father Alphonse begged a taxi driver not to take his son to his former school because he feared he was armed with a knife and planning an attack.
Reading a statement on behalf of the Stancombes, Nicholas Bowen KC, who is representing the three grieving families, said: "When a parent knows their child is dangerous, allows them to possess weapons and authorities have already visited the home, how is that not neglect?".
"If a child were malnourished or unwashed, social services would act immediately. But when a child is surrounded by weapons, involved in violent behaviour and known to be a threat, the system does nothing. That is a failure. No action was taken. Why? Our daughter paid the price for that failure. When does a parent become complicit in a crime committed by their child?".
The murderer was sentenced to life imprisonment with a minimum term of 52 years in January at Liverpool Crown Court, after admitting to the "sadistic" murders and attempted murders.
Nicholas Moss KC, the counsel for the inquiry, stated that the proceedings would provide a "definitive account" of the attack, its background and the perpetrator's interactions with state agencies, including the police, schools and social services.
Sir Adrian Fulford, the chairman of the inquiry, has vowed to do everything "humanly possible" to address the queries of the grieving families and victims. He further stated: "What occurred on that day has made it critically necessary, moreover, to identify all the changes that need to be implemented in order to ensure, as best as our society is able, that there is no repetition."
The first phase of the inquiry is anticipated to carry on until November.
You may also like
Top 10 most complained-about shows this year finally unveiled
Black Rabbit filming locations as Jude Law Netflix crime thriller drops
Madeleine McCann suspect Christian Brueckner 'almost under house arrest' says top cop
Perfume fans are 'obsessed' with 'dreamy' new citrus scent at Cult Beauty
Man Utd 'don't need' £62.5m signing as Ruben Amorim told player can save season