Big Cats in Australia?

For a few years I've been researching reports of big cats in Australia, usually black panthers or cougar like creatures. About 5 years ago, when I was 9 or 10, me and my friend's whole family heard something that chilled us to the bone. Me, my friend and her teenage brother were playing outside waiting for dinner when we heard this indescribable, freaky scream/howl type noise. And this EXACTLY what it sounded like: a href="http://www.youtube.com/watch?v=xKw4OFAu1WM" rel="nofollow"http://www.youtube.com/watch?v=xKw4OFAu1…/a it's of a female cougar in heat. The second was early this year, we were in the Stirling Ranges of Western Australia having lunch, when I followed my little brothers down a bush track because they'd run off and we were leaving soon. I got that feeling that something was watching me and as I turned around I saw a huge big black panther like creature running off into the bush. It moved with a very graceful and fluid motion, the main things I remember where how long its tail was and how heavy it sounded as it bounded off. And the last encounter was with my brother. We were walking back down the hill to our car (this was again around the Stirling Ranges) when my brother screamed and shouted for us to come quick. He was way up ahead and when we reached him he looked like he'd seen a ghost. He said that he saw a black panther stalking him from the bush and when he screamed and started throwing rocks at it, in ran off. We could all hear it running through the bush. It was not a kangaroo and didn't fit the description of any other native Australian animal. So what is your opinion on this? Are there any big cats living where you are that aren't supposed to be there (like leopards in England)? Have you had any encounters with them? (especially if you live in Australia). And no rude or stupid answers please. Thanks in advance.