French anti-terrorism police on Tuesday detained seven people suspected of having communicated via social media with the killer of a schoolteacher whose beheading last year reopened debate about France's cherished rights of expression, a judicial official said.

The teacher, Samuel Paty, was killed Oct. 16 outside his Paris-region school after showing caricatures of the Prophet Muhammad during a class debate on free expression.

His killer, identified by authorities as Abdoullakh Anzorov, was later shot dead by police. Anzorov, an 18-year-old refugee of Chechen origin who had become radicalized, according to authorities, claimed responsibility for the slaying in a text found on his phone that was accompanied by a photograph of the teacher.

Read more: ABC News