Fatal shots fired at six brumbies in a NSW state forest appear to be the work of an experienced marksman, police say.
Four stallions and two mares were found shot dead in the Newnes State Forest near Lithgow on Sunday afternoon.
Police are now hunting for those responsible for the illegal culling.
Lithgow police Inspector Gerry Cahill said it appeared the horses sustained head shots from an experienced marksman.
"There was no evidence of (horses) kicking afterwards," he said.
It appeared to have been done very quickly, Insp Cahill added.
Investigators also believe a high-calibre rifle was used.
Insp Cahill said police would question people who were permitted to hunt in the forest on the weekend.
Illegal hunting on private property can attract a $1100 fine or up to 12 months in jail, he added.
Aerial culling was banned in NSW in 2000 after outrage over the mass shooting of more than 600 horses in northeastern NSW.
The cull was conducted by the National Parks and Wildlife Service over three days in the rugged Guy Fawkes River National Park.