Elmer and his wife, Emma, had once planned to leave American-controlled Manila and return to their homeland shortly before the Japanese attack on Pearl Harbor occurred. The Japanese invasion succeeded it in no time and involved the couple, too. Elmer died on April 17 (or in July), 1942 in the Santo Tomas Internment Camp in the Manila, Philippines, of natural causes. His private type collection, held in the Philippine National Herbarium, was destroyed about that time. Emma Osterman Elmer survived internment.