Bill Clinton joined hundreds of people to mark the 20th anniversary of the 1995 Oklahoma City bombing Sunday, remembering the 168 victims killed in the federal building explosion. The ceremony took place outside the Oklahoma City National Memorial and Museum, which stands on the grounds of the leveled Alfred P. Murrah Federal building and where a permanent display of 168 empty chairs symbolizes each victim. Clinton, who was president at the time of the tragedy, joined relatives of victims and survivors to decorate the chairs with flowers and mementos. Anti-government militant Timothy McVeigh was convicted on federal charges and executed for carrying out the bombing. His accomplice Terry Nichols was given multiple life prison sentences.