arnold new this would be a high profile case. he didn't know it would be the case of a lifetime. >> today's date is may 18,2006. >> reporter: a video camera rolled as detective arnold processed the crime scene, honing in on clues. >> this drum, near the victim's body, a shell casing. >> reporter: the harsh reality of death lay side by side with the every day images of young life. erin's body in a pool of blood, near a red kiddy wagon. a shell casing in front of a box of diapers. and the bed where erica jumped for joy was covered in her own blood. >> suspected blood on the sheets, pillows and pillowcases. >> reporter: detective arnold noticed something on the bed. >> the first thing that immediately hit me was the dora the explorer pillow with blood