Sara Bermudez, 38, and her three children, Madison, 8, James, 6, and Michael, 2, are viciously attacked in the middle of the night while they sleep. The murderer Sexually assaults Sara and her 8-year-old daughter, with a knife and stabs the family to death before setting them on fire. Sara's father finds the carnage and calls for Help. Investigators catch a break in that the killer tried to use diesel to fuel the fire but it burned itself out before totally destroying all the evidence. Joseph Scott Morgan is going to take you inside the master bedroom and explain how investigators find a suspect from a portion of body fluid left behind at the scene. And the suspect isn't just close to the family, he is family.    Transcript Highlights00:00.96 Introduction - chewing and identity04:20.45 Somebody breaks into a home in the middle of the night Slaughters the mom, daughter, two boys09:20.18 Family murdered and set on fire14:12.60 Disturbing element to the case 18:12.07 Setting up a line to prevent contamination22:57.18 Evidence of sexual assault28:07.64 Knife used in sexual attack32:56.90 Blood stains found on walls, carpet, lamp, other items37:12.63 Finding blood in the fire42:00.92 Mother defended her children44:58.66 ConclusionSee omnystudio.com/listener for privacy information.