2/ The Gestapo is considered to be a creation of Hermann Goering, also of Luftwaffe fame. Control was given to Himmler in 1934. This Feb 1936 law gave it carte blanche to do whatever it liked. . . all without judicial review. 
3/ "Secret Police can carry out investigations in cases of High treason, treason, crimes connected with explosives, as well as other attacks on Party or State. . .has the competence in cases of violation of law concerning firearms and ammunition. . .administers all conc camps."
4/ It's a safe bet that while this law was being drafted, everyone was busy with activities of daily living, all hoping for the best, many nourishing the hope that it would "all blow over" and things would return to normal. Very few saw what was coming clearly.
5/ According to Laurence Rees, 80% of Gestapo investigations were triggered by denunciations by members of the public. It's not clear (to me) how many 1000s of people were imprisoned by them, but it is stated that thousands disappeared while in Gestapo custody. (pic: Krakow)
6/ The former regional Gestapo HQ shown here, known as the EL-DE Haus, is now the NS-Dokumentationszentrum Köln, a museum documenting the Third Reich. The building was the site of many executions. @NSDOK
