NEWARK, N.J. (AP) — For what seemed a small eternity, Shalga Hightower epitomized the picture of parental grief in the aftermath of Newark's 2007 schoolyard killings, when a group of men and boys, including one who turned 15 that day, lined up her college-bound daughter and two friends and shot them each in the back of the head. Recently, she embarked on a documentary film project that highlights the struggle of families victimized by gun violence, through the prism of her own experience. Six men and boys accosted and robbed the four friends as they sat listening to music on the Mount Vernon School playground. Terrance "T.J." Aeriel, Dashon Harvey and the survivor — whom The Associated Press isn't identifying because of the sexual assault — had played in their high school marching bands in Newark and already attended Delaware State. For Hightower, that meant watching from the gallery as autopsy pictures of her daughter were displayed that showed her head wounds from the machete. Eventually, all six defendants, some of whom had ties to the MS-13 street gang, either pleaded guilty or were convicted, with some sentenced to hundreds of years in prison. The killings spurred anti-crime efforts in Newark that were credited with driving down the murder rate over the next few years.