A Maryland man has pleaded guilty to threatening to murder a member of Congress who supported legislation he opposed, Justice Department officials said Friday.

In a plea agreement, Darryl Albert Varnum, of Westminster, admitted to leaving a threatening voice-mail message at the Florida office of a House member, who officials did not identify.

“We take violent threats extremely seriously,” Robert K. Hur, the U.S. Attorney for Maryland said in a statement.

Varnum, 43, was arrested in July. He faces up to five years in prison, officials said.