Viola Davis and Jennifer Lopez are grief-stricken mothers in Lila and Eve, which premiered Friday night at the Sundance Film Festival. Lila Wolcott, played by Davis, is broken when her 18-year-old son is gunned down in the street — an innocent victim in the wrong place at the wrong time. At a support group for parents of murdered children, she finds a kindred spirit in Eve, played by Lopez, who’s more interested in getting justice than talking through her problems. Davis, who is also a producer of the film, said she was drawn to the role because it brings to light something rarely discussed in violent American culture: How do parents whose children have been killed move on?