Richard Milhous Nixon (January 9, 1913 – April 22, 1994) served as the 37th president of the United States from 1969 until 1974. Four of the five Nixon boys were named after kings who had ruled in medieval or legendary Britain; Richard, for example, was named after Richard the Lionheart. Further protests erupted against what was perceived as an expansion of the conflict, and the unrest escalated to violence when Ohio National Guardsmen shot and killed four unarmed students on May 4. Nixon's responses to protesters included an impromptu, early morning meeting with them at the Lincoln Memorial on May 9, 1970. It is estimated that between 50,000 and 150,000 people were killed during the bombing of Cambodia between 1970 and 1973. Richard Nixon's Presidential Library and Museum located in Yorba Linda, California.