The Nazis gas vans were hermetically sealed trucks with engine exhaust diverted to the interior compartment. Use of gas vans began after Einsatzgruppe members complained of battle fatigue and mental anguish caused
The Nazi Kripo (Criminal Police) | Holocaust Encyclopedia
The Liberation of Majdanek | The National WWII Museum | New Orleans
Gas chamber - Wikipedia
Final solution | Definition, Holocaust, & Third Reich | Britannica