Mutation analysis is being extensively used for testing from a finite state machine (FSM); it consists in seeding a fault in the model using a mutation operator. There is still a lot that we need to know about mutation fault for FSM so that we can adequately use them in software testing or in software testing experiments. In this paper, we report on results from an empirical experiment during which we compared different mutation operators used to generate mutants from an FSM. We randomly generated multiple FSMs along with all the possible mutants from a relatively complete set of mutation operators. We then generated test suites using transition trees which are then executed on the FSM and its mutants to measure the mutation score for each mutation operator using different types of oracles. In doing so we report on how easy, or difficult, mutants generated from specific mutation operators can be. We have developed a tool that automates the whole process of this experiment.