"Death camps" as such weren't introduced bybthe Nazis until after the war had started, along with other extermination methods directed at Jews and Gypsies. Without the war it seems unlikely they would have happened in that form.

But there was plenty of persecution and murder of Jews and Gypsies. Most dramatically, for Jews, during the Kristallnacht pogroms in 1938.

The evidence was there, but a lot of people chose to look the other way. Not just ordinary people who were dependent on what the mass media chose to tell them, but the kind of people who controlled what went into the mass media.