An interactive exhibit in Mississippi prompts visitors to speak aloud the names of people who were killed in acts of racist violence in the United States during the civil rights era — incantations in a darkened room to honor some 150 men, women and children whose lives were cut short. The names appear on lighted glass panels, backed by images of trees. Next to each name is a code that visitors can scan with their cellphones. The exhibit is on display until Oct. 24 at the Two Mississippi Museums in downtown Jackson.