in what sense is pimpernel's death ironic?

Pimpernel, along with Holly and Bluebell, actually escape from the Sandleford warren with their lives. When they finally reach Cowslip's warren they are attacked because of their association with Hazel. THe rabbits there attack the trio and kill Pimpernel. THe irony is that Pimpernel escaped one warren only to be killed in another.