We used to do this in Habbo Hotel. I don’t know how RuneScape worked back then but in Habbo you could buy virtual furniture dropping their valuables into one of our rooms and then kicking them out and making the room private. So, it is different from your example in that “killing” was by-design meant to take stuff from other people, whereas what we did was closer to “fraud” (good luck regulating that in 2006) as other comment said.