Joshua Dunn. PPDA cold case has been closed.Joshua Dunn, 23, was arrested Tuesday after turning himself in for a two-year-old murder, police said.Dunn shot 27-year-old Franklin Lewis to death on July 18, 2011.The case was one of Philadelphia’s unsolved homicides.No motive was given for why Dunn, of the 6100 block of North Fourth Street, killed Lewis, of the 200 block of East Shedeker Street, or for why he decided to turn himself in.Dunn was arraigned today, according to court documents.He faces charges for murder and possession of a gun.____________________Follow Sam Newhouse on Twitter:@scnewhouseFollow Metro Philadelphia on Twitter:@metrophillyFollow Metro Philadelphia on Facebook:Metro Philadelphia