Using guns to move people into the chambers was less traumatic than lining them against the wall and shooting them.

The genocide ended with the victory of the rebels led by Kagame. They were mostly Tutsis.

The armed Tutsis did indeed hit back.

The Nazis built the gas chambers because shooting crowds of women and children was giving their low end grunts PTSD, even the hardcore SS. They needed something where you didn’t have to watch them die.