Not true: the former border police (Bundesgrenzschutz, parent organization to the famous GSG 9) has been officially the Bundespolizeit (federal police) since 2005, and there has always (well, since the 1951) been a federal investigation agency (Bundeskriminalamt). Most claims of police violence are actually against the Bereitschaftspolizei (riot police units, exist both at state and federal level), which is not surprising since they are deployed (and trained) mainly for potentially violent situations.
To clarify: I know there are federal investigative police (but not as powerful as the FBI, right?) so I deliberately used the verb, meaning enforcement. I didn't know there were federal riot police though.
