It was a good question, since the Doctor was a pacifist and didn't want to use violence until it was a last resort thing. Caitlyn ate her food looking curiously at the Doctor wondering what he would do.
Rose was just as curious drinking her tea. She considered the options herself. There weren't many options open for a psychopath. They wouldn't be able to change him and if they tried to keep him so he wouldn't harm anyone, it might work for a time.