The latest suspect was nabbed by ABW officers in the northeastern city of Olsztyn under an investigation led by the district prosecutor, said Jacek Dobrzyński, spokesman for the country's security services.
Two other 19-year-olds were detained in April.
“The three young men planned an attack on a school and were fascinated by an ideology that spreads terrorism,” Dobrzyński told reporters.
He added that the suspects studied mass shootings in Norway, New Zealand and the United States.
They downloaded bomb-making manuals, practiced shooting “in open terrain and inside buildings” and acquired pyrotechnic materials, he said.
(jh/gs)
Source: PAP