The arrest took place just as the material was delivered to his house, the statement said.
Police said they had been watching the man for the past five months after messages referring to Columbine began appearing on Internet pages in Spain.
A police spokesman said the suspect had previously studied electronics at a technical training school and had recently begun a course in business administration. He said he earned money by playing poker on the Internet and had recently moved out of his family house and into an apartment.
The officer spoke on condition of anonymity in keeping with police regulations.