They'll use the FEMA camps in the exact same way the Nazis used the ghettos. They'll tell the inmates that they need to be there for their own safety, kill anybody who tries to escape, exploit the inmates for free or low-cost labor, and take their time killing them off at the statists' convenience. Like the ghettos, some people will successfully escape, only to realize that life on the outside can be just as hard if not harder than life in the FEMA camp, and then sneak back inside for the "comfort" of the camp.
Read the book "Defiance." Don't just watch the movie. The movie is good, but extremely over-simplified. Read the book.