it's highly possible that the 'motive' makes perfect sense to Holdom... .. on the other hand, it is just as likely that he himself has no idea. Cant even explain it to himself.. ( I think this last one a remote chance, but even so, it cant be rejected )...
What stumps me, is how that point of murderous rage was got to, twice , on two different people, one an adult, one a baby, with a time lapse in between, at two different locations ( thanks to the person who reminded me of that ) .
Assuming.. (just for today) that he used some mind altering element to get to the rage enough to kill Karlie.. and to subsequently bury her. ( two different activities at two different times )
And then he has to get to that point again to murder Khandalyce... He already knows he can kill. Successfully and undetected, , it would appear, so when it comes to Khandalyce he is ahead of the game, it isn't unknown territory, it is very recent and familiar.
So he lets loose... or someone else does? someone else who , also, can achieve that particular pitch of rage right on cue.
I don't believe Karlie was actually buried. I think this is important to an extent, as it could indicate a certain psychology aspect to the crime - being left at a scene, as opposed to the offender spending time actually digging a grave to better hide the remains. Although, the offender may have intentionally left Karlie's body in a similar fashion to Milat's victims, to give pause for the police to suspect the murder was connected to Milat.
"Everything was tucked away behind a log."
http://www.smh.com.au/nsw/human-sku...belanglo-says-trail-biker-20100829-13xrq.html