He didnt know that they were. They may have been working people to death, or hadnt geared up for the final solution. Sounds like bullets were used to kill prisoners before the arrival of the US forces.
Leon Morin helped liberate Dachau according to this letter he wrote home.
According to Morins description the prisoners were gassed.....
If you were there, Gitmo and gundog I would give you the benefit of the doubt....
But Morin was truly there.....I believe the letter......there is too much history of Dachau not to