State/Government-organized stalking, tortures, assassinations, massacres, terrorisms, mafias' creation and management are possible since the management, cover and cooperation of the Quirinale (the Presidency of the Republic), the formal government and the Co.Pa.Si.R.
In Italy, the main police (Presidential Guard too), with various Secret Police departments and officers, is the Carabinieri. It is not a civilian police. It is a military corps of the Defence Ministry, at the same level of Army, Navy and Air Force.
Differently from the civilian police (the PS - State Police or Police of [the] State), which mainly is urban, the Carabinieri are urban and rural (since that, they create and manage not only urban mafias but also rural ones). The Carabinieri de facto supervise the civilian police. They belong to and de facto supervise also the main Secret and Information Services. Italian main Secret Services are inter-force ones (Carabinieri, PS, GdF etc.)
The Carabinieri are the main structure of whatever form of State Terrorism.
Another relevant military and police structure (of the Ministry of Economy and Finance) is the Fiscal Police [Guardia di Finanza / Finance Guard]. As the Carabinieri, the PS etc, it is also used as judiciary police and it can be employed for State Terrorism. http://en.wikipedia.org/wiki/Guardia_di_Finanza
There are various other police services. All of them have, as wherever in the world, Secret Police departments and officers, with special regulations and powers, and covered from the State Secret.