The first nazi concentration camp was founded in 1933, gas chambers and systematic killing were only added in 1941 when the "final solution" was implemented. Those last four years are the most well-known period, but for the majority of Hitler's rule concentration camps were just what it says on the tin: camps where undesirables were concentrated. Places that became overcrowded, hotbeds for disease, labor camps and places of medical experimentation. Plenty of people died there even in that period, but from causes like illness, work accidents, malnutrition and bad medical care.

ICE detention centers are not comparable to a 1942 nazi death camp, but comparisons to a 1939 concentration camp seem apt