elusive killer dubbed the grim sleeper. it was the 1980s, a serial killer was terrorizing south los angeles. most of his victims were young african-american women, some had been shot with the sam same .25-caliber firearm. some had been strangled, some sexually assaulted. their bodies dumped in alleys. over the years, los angeles police would follow numerous leads that went nowhere. in 1988, after eight murders and an attack on a potential night victim who got away, the killings stopped. then nearly 15 years later, the grim sleeper would strike again. who was he? where was he hiding? police would have to wait another two decades to find the answers. >> we have about one and a half million samples stored in the laborato laboratory. >> a critical piece of the puzzle would be found here in the third-largest dna rository in the world. california has been collecting dna from convicted felons since