SAO PAULO — Authorities arrested a teenager Tuesday for allegedly being involved in planning a school shooting in which eight people and two attackers died.

The police officer in charge of the investigation told Globo TV that he believed the teen was one of the masterminds of the bloodshed.

"He is an intellectual mentor. He bought objects that could allow him to participate in that crime," said officer Alexandre Dias with the local police unit in Suzano, a suburb of Sao Paulo, Brazil's largest city.

The Suzano police unit was not immediately available to comment.

The 17-year-old male, whose identity was not released, was described as a former student at the Raul Brasil public school in Suzano. The teenager was questioned last week but was initially allowed to return home.

Sao Paulo's Court of Justice said Tuesday that the teenager was ordered held in a jail for juvenile criminals for at least 45 days.

Attackers Guilherme Taucci Monteiro, also 17, and 25 year-old Luiz Henrique de Castro killed themselves after killing seven people at the school. One of the attackers also killed his uncle, who owned a nearby used-car dealership.