The Department of Sustainability and Environment are investigating the March 28 attack where the kangaroos were bailed up and rammed by a car, shot and mutilated.

Australian Society for Kangaroos vice president Fiona Corke said four kangaroos were found dead at the scene, while another two had to be euthanased.

She said an alive female kangaroo was found riddled with shotgun pellets, while another male was found crawling across a paddock after both its hind legs had been broken.

Ms Corke said one kangaroo was found beheaded.

"It is absolutely disgusting, horrific and appalling -  I don't know what sort of people would do that," she said.

"It goes along with some of the worst cases I've ever seen, particularly in terms of the mutilation and dismembering of the animal.

"Rescuers have been trying to find the two missing joeys but they haven't been able to locate them and they probably won't be able to survive."

Ms Corke said people who brutally killed kangaroos for 'a thrill or a bit of fun' faced harsh penalties.

She said Australian wildlife, including kangaroos, were protected by law.

"Whether these people had a permit to kill kangaroos or not, the use of a shotgun is illegal," she said.

"People need to know that there are eyes and ears out there and they will be caught and face extremely high penalties."

Ms Corke said the couple who found the kangaroos and called the society were traumatised by the experience.

"It ruined their whole Easter just because of what they saw," she said.