The man was plotting an attack on a particular group of people based on their nationality or religion, the Tarnobrzeg District Prosecutor's Office said on Friday. The plan was intended to be in support of the objectives of ISIS and like-minded extremist organizations, authorities said.

Weapons manuals and assassination plans discovered
The teenager was in possession of copious material on terrorist tactics, prosecutors said. This included tutorials for firearms, explosives and incendiary devices, poisons and bomb-making. They also found an assassination list with the names of people and the firearms meant to execute them.

Prosecutors said the suspect had made notes for an attack on a school in the Podkarpackie province. Though the teenager conceded he was inspired to violence during questioning, he disputed he was preparing for a terrorist act.

It could have up to a decade in prison for charges
The 17-year-old has been indicted for preparing a mass attack, incitement to hatred and online dissemination of propaganda for jihadist violence. He has been detained pending investigation for three months. If found guilty, he could be sentenced to 10 years in prison.

Prosecutors emphasized that the investigation is continuing and that other evidence is being examined to establish how much he actually carried out.