Spielberg, Capshaw and Katzenbergs also donate $500,000 to ‘March for Our Lives’ rally organized by Florida students A number of Hollywood heavyweights, including George Clooney and Oprah Winfrey, announced hefty donations Tuesday to help fund the “March for Our Lives” rally against gun violence that is being organized by students from Marjorie Stoneman Douglas High School in Parkland, Fla., the site of last week’s massacre that left 17 students and staff members dead.Clooney and his wife, human-rights attorney Amal Clooney, announced a $500,000 donation Tuesday morning to help offset the costs of the march in Washington. “Amal and I are...