Mario Cerciello Rega: The story behind Italian police officer's killing

Italy has been rocked by the killing of a plain-clothed police officer in Rome. There has been an emotional outpouring of grief for him.

Mario Cerciello Rega was stabbed in the Prati neighbourhood on 26 July while attending an incident.

The story of his death is a complex one, as BBC News Europe reporter Gavin Lee explains.