However, Son Sen, who was responsible for National Security and Defense and Ducha commandant at S-21, were directly responsible for killing the prisoners at S-21 and Cheung Ek Killing Field and written proof is available.
Then, with the electricity light supplied by a generator , Peng or Huy the heads of capturers subunit, verified prisoners’ names against a "must-smash" list prepared by the head of documentation unit, Suos Thy. This list ensured that no one prisoner was missed. Prisoners were led in small groups to ditches and pits that were dug in advance by another team stationed permanently at the site.
S21 Victims - The Killing Fields Museum of Cambodia
This lie was created to prevent the prisoners from crying, refusing to go or from escaping. In order to be well prepared for execution, a messenger from the defense unit was sent to the Choeung Ek Killing Field in advance to inform a permanent team about the number of the prisoners to be killed that day.