Republican lawmakers told Attorney General Eric Holder on Thursday to fire some Justice Department subordinates over the flawed arms-trafficking investigation called Operation Fast and Furious.

At a House Judiciary Committee hearing, Rep. Jim Sensenbrenner of Wisconsin said impeachment is an option if Holder does not “clean up this mess” quickly.

Sensenbrenner and other Republicans hold the attorney general responsible for the operation, in which federal agents failed to track illicitly purchased weapons that were later recovered in Mexico and the U.S., many of them at crime scenes.

“If you don’t get to the bottom of this,” there is only one alternative, and “it’s called impeachment,” said Sensenbrenner, without specifying whom he had in mind.