If the Greek police had any brains they’d find the neighborhoods where these kids are living and force them out or arrest all of them. Execute them if they have to.
Up until this incident, I believe the intent of the bombers was, as mentioned, property damage and they have been careful to minimize the potential for injury to people. This, in turn, has permitted a tolerance in pressing these groups by the authorities. Now they have rather deliberately targeted a person and have killed a police officer.
The rules of the game are about to change...