The sister of Republican presidential frontrunner Donald Trump received a threatening letter, the FBI said Sunday. The letter was sent to Judge Maryanne Trump Barry, who sits on the U.S. Circuit Court of Appeals for the 3rd Circuit in Philadelphia. The FBI said it was was working with Secret Service and U.S. Marshals Service regarding the incident. Last week, Trump’s son Eric also received a letter, which threatening to harm the business mogul’s children if he doesn’t drop out of the presidential race, authorities said Friday. The envelope was sent to Eric Trump’s Manhattan apartment and contained white powder, which was determined to be non-hazardous.