To me he definitely looks like a cane toad juvenile. I have several Australian herpetology field guides and he seems like a match to me. It also appears to be a toad from the family Bufonidae, which the cane toad is the sole species of in Australia. Based on documentaries I've watched its not uncommon for cane toads to flood into new areas because they are an invasive species. In reality killing them has little impact on their explosive reproduction and more people have gotten hurt by killing these toads then successfully eliminating them. I completely understand why people kill them but it's not their fault they are stuck in Australia so I also feel kinda bad for them. The most humane way of killing them that I know of is throwing them all in a bag and freeze them because they are cold-blooded so they constantly adjust themselves to the temperature until they fall asleep forever. I personally wouldn't kill them because I'd feel bad if I did.