Yes, It's A Mental Illness...

 ...and it often goes hand in hand with other expressions of mental illness:

A murder-obsessed teenager who spoke of carrying out a mass shooting at an Edinburgh school has been jailed for six years. A court heard Felix Winter, who is now 18, "idolised" the killers behind the 1999 Columbine High School massacre in the US. The pupil repeatedly spoke about mounting a similar "Doomsday" attack to the one which claimed the lives of 12 students and a teacher in Colorado. Winter, who also held racist and pro-Nazi views, admitted two charges at a hearing in February.

But no matter what someone’s been found guilty of, there are always those eager to assist them to escape punishment. 

Shelagh McCall KC, defending, called for a strict alternative to custody as her client was a "vulnerable young person" with mental health issues.

Indeed so, more so than this article wishes you to realise: 

Police Scotland launched an investigation in the summer of 2023 after a social media photo of Winter at school wearing combat gear and carrying an imitation gun caused panic among pupils and parents. It emerged the clothes and prop gun were issued to him for a video being made in a drama class in which he had been cast as a kidnapper. But detectives established Winter, of Kirknewton, West Lothian, frequently spoke to other pupils about carrying out a school attack.

Officers discovered that the schoolboy had a TikTok account which had footage of him wearing black combat clothes as well as a skeleton mask.

Despite the name and the pronouns used by the BBC, this is a girl. 

At a previous hearing, Winter's lawyer said that the teenager was vulnerable and a transgender person and that would need to be taken into account.

Quite why, when it’s merely another facet of her extreme mental illness, God only knows!