David Rossi:  I was here on a serial rapist in ' _ 88 _ . It was pretty short work . The guy was n't gon na win any IQ contests . The day after we , uh , collared him , a local detective was driving me to the airport , and , um , he hears a call on his walkie of kids screaming in a house not far from where we were . He asks if I mind taking the job in with him . We were first on the scene . Inside we found ...
Derek Morgan: Found this .
David Rossi: The ax had been left behind , but it had been wiped clean . It turns out it belonged to the family . The , uh , oldest daughter , Connie , told me her father bought it on Christmas Eve a few months earlier , to cut down the Christmas tree . Now I , uh , always associate the whole thing with Christmas . Never been able to put a tree up myself again .
Jennifer 'JJ' Jareau: So he ... he never hurt the kids at all ?
David Rossi: Not physically .
Derek Morgan: But he would have known that the kids were in the house .
David Rossi: He only hurt the parents and then left .
Emily Prentiss: Okay , so using a weapon he found at the scene and not eliminating all of the potential witnesses , that makes him disorganized .
Derek Morgan: But he left no evidence , which suggests he 's organized .
Jennifer 'JJ' Jareau: There was a fingerprint .
David Rossi: But it was behind the bedroom door . I do n't even think he knew it was there . There should have been prints in other places , but they were wiped clean . An open back door , a ... a drinking glass left in the kitchen . And that one good print ... was not a match anywhere . I 've been over this a million times . I ... I keep thinking if there was just one more piece , one more thing to go on . The answer was right in front of me .
Emily Prentiss: He might be dead .
David Rossi: I have to be sure .
Derek Morgan: Rossi , if he 's dead , you may never really know .
David Rossi: When we arrived on the scene ... before any of the other units got there , I could hear them ... before I even got out of the car . It was a warm morning and the , um , the windows were open in the upstairs bedroom . And their voices ... floated out into the street . They were crying and calling for their mommy and daddy . Three terrified children screaming for their murdered parents . I 've seen so much death and pain , but that sound ... it 's been twenty years and I can still hear them screaming every night ... crying . If I ca n't tell them for sure that whoever 's responsible will never do it again ... that screaming might never stop .