Why didn't Wehrmacht Soldiers refuse to execute civilians (and Kids) when it was clear that they did nothing wrong? 

I know that they were probably told they're partisans or Jews or something along those lines but still I find it hard to believe that so many soldiers executed them for no real reason.

Also how did those soldiers deal with the stress that obviously comes alongside executing innocent people? 

Are there any known suicides or mental breakdowns of Wehrmacht Soldiers after such executions? 

How did the generals deal with those refusing to shoot?