(CNN) -- Tracy Martin, Trayvon's father, told CNN's Anderson Cooper on Thursday that his children had grown up in a diverse community, so he didn't feel a need to have a conversation about how Trayvon and his other son should deal with race. Rather, he said he talked with his children about "how we prepare them to become teenagers, to become upstanding citizens, to conduct themselves in public." But once his unarmed son was shot, he said that changed. "What is it I can tell my child now?" he said.