Nobody really knows if they were plotting against him but that's what he thought and Gobbles told the world. One of the leaders that was killed was Rohem, he was the leader of the SA and was planning on uniting with the army, Hitler couldn't have this because he would have become too strong, and so to stop him he killed him.
I think the sources are totally different from each other and can both be seen as biased. .
Source Ca is a statement from Goebbels, Hitler's minister of propaganda, Goebbels and Hitler were in on it all together and probably wrote it together. Some of the story could be true but in this source only from Hitler and Goebbels point of view, a sick, deceitful and manipulative point of view, this is how the Nazis put their point across. That is why I think this is a biased source and cannot be trusted. Hitler and Goebbels were brilliant at launching propaganda for themselves and the Nazis, so you cannot trust this source to give you the real details of what really happened on the night of the long knives, you will only get what puts the Nazis in the best light, this is what Hitler and Gobbels always did, they turned things round to put things in their favour. .
David Low, a British cartoonist, has drawn source Cb. This source can be classed as biased because of the two different governments at that time, the British were in a democratic government at that time, the Germans were in a fascist government. These two governments had totally different views, laws and believed in different things, so each country would send out black propaganda for the other country. .
There are some true points that match in the two, Hitler is present, although Goebbels makes it sound as if Hitler single handedly marched in and saved the world from such vile scenes, another example of what the Nazis did to turn the propaganda in there favour, it does appear that he was present. There are also things that don't match up, Ca says that the SA deserved to de treated like they were, Nazi propaganda, were as Cb is saying they didn't, difference in the two governments views, there is one thing that becomes apparent, Hitler disposed of people when he didn't need them any longer.