Theory
Firstly - Sad news today and everyone I am sure has their thoughts for this young mans family and friends - and the operators at GEA.
In response to Virtually There: "cargo flight = too heavy to get airborne; EFAT "dead man's turn" (might explain witness statements about "spinning" aircraft and why they were looking for him out over water); somatogravic illusion = nose down instead of up"
Let me see if I can offer something
1 - Cargo flight too heavy - That run leaves Broome with about 20 to 50 kgs of freight it would never be anywhere near MTOW on Dep at BRM.
2- Somatogravic illusion - I would suggest no. I have departed BRM RWY 28 at night and I got it once, I actually had to talk to myself out aloud as I climbed away the feeling was very strong and I can see why pilots have died in the past. But the photos of the wreckage don't seem to support this.
3- EFATO - I would say most likely. The photos show the left engine (separated from the mounts) with one of the blades undamaged, this could indicate that the blade wasn't spinning at the time of impact - However the blade doesn't appear to be feathered.
The nose of the aircraft is facing East not to the West. This would also support the aircraft spinning in. The aircraft seems to be in a very small location indicating it wasn't at a shallow body angle on impact.
HOWEVER - all this is speculation and the ATSB will do their job and work out why this young man paid a very heavy price for doing something we all love.