The 18-year-old youth picked up in December for planning to carry out a school shooting has been given a one-month juvenile detention term for ‘threatening behaviour’ by judges in Amsterdam.

Mitchell O has already been held in custody for more than three months and will now be released but will not be compensated for the extra time he was in detention awaiting trial, the AD said.

During the trial it emerged Dutch police were alerted to him by the FBI and he had also been spoken to by police about his online behaviour. O told judges that the threats which led to his arrest were ‘a joke’.

O was arrested after placing a English-language video on YouTube saying he was making preparations to shoot at a school. On his phone were films of school shootings, bomb attacks and other incidents.

A psychologist and psychiatrist have both assessed O and found him to be suffering from a form of autism, the AD said.

A spokesman for the public prosecution department stressed that the teenager had not said any particular school was a target.