How were they killed at the concentrtion camp?
Methods of killing people in the camps became very inventive, but most would have died as a result of being under-fed and over-worked, they would have died of starvation, exposure, disease and illness, not to exclude those who were beaten to death, or died from industrial accidents. (as opposed to those who were gassed in the extermination camps).
Westerbork sent them to concentration camps like Auschwitz there they were killed. <><><> Westerbork- the camp when Anne Frank was sent- was a transit camp. People from that camp were transported to other camps, where they were killed, usually by poison gas. Link at the bottom of this page to an article on Westerbork-