My thoughts are somehow he had knowledge that Boak Rd ( Telstra tower area) is the turnaround half way point of her 14 Km run and lay in wait .
I agree, I think he has watched Sam before and this might have been planned for a while
Police thinking it was a targeted attack
for someone supposedly off his face
he has been methodical in planning, organising
He would have known there would be a big search team looking for Sam in the next hours
Including helicopters, fixed wing, extra police on the roads, leading into the bush etc..
So his getaway with Samantha, my thinking quick and to get out of there
with possible at this stage Samantha semi-conscious / unconscious in his vehicle
Depending on what his girlfriend has said to police, how long he was away for when questioned,
The police might be able to obtain intelligence through conversations/messages between him and his girlfriend listening into the conversations on the morning of Samantha's disappearance, through to her sadly death
He could have travelled anywhere, Geelong is only 1 hour via highway from Mt Clear
If anyone asked, including his girlfriend, where he is going before 8am,
he could mention to her and others, lying, that he's going to do an emergency electrical job somewhere ( being an electrician ) and will be back later on