Federal prosecutors say an improvised explosive device directed at former U.S. Attorney General Eric Holder Jr. was addressed to his office at a Washington, D.C., law firm, but ultimately delivered to a return-to-sender address in Florida. Holder is a partner at Covington & Burling.

Prosecutors on Friday charged Cesar Altieri Sayoc with mailing approximately 13 packages containing explosives with the intent to injure prominent former public officials, particularly those closely associated with the Democratic Party, according to a complaint filed in the Southern District of New York.

“The intended targets of the defendant's IEDs included former President Barack Obama; former Vice President Joseph Biden; former Secretary of State, former Senator, former First Lady, and 2016 Presidential Candidate Hillary Clinton; former Attorney General Eric Holder; Congressperson Maxine Waters; Senator Cory Booker; former Director of the Central Intelligence Agency John Brennan; former Director of National Intelligence James Clapper; philanthropist and billionaire George Soros; and actor and director Robert De Niro,” the complaint states.

The complaint identifies Holder as a partner of a “certain law firm” without mentioning Covington & Burling by name, and notes that the IED was addressed to Holder's office at his firm in Washington, D.C., described as “Holder Office-1.” Holder returned to Covington & Burling in D.C. in 2015 after leaving the Department of Justice.

The package directed to Holder was returned this week to the sender's address listed on the package, which the complaint alleges identified as belonging to Debbie Wasserman Schultz, a Democratic congresswoman in Florida and former head of the Democratic National Committee.

A Covington & Burling spokesman declined to comment on Friday and referred all questions to law enforcement, as the firm has done continuously throughout the week amid earlier reports of a suspicious package directed at Holder.

Law firms across Washington, many of which are home to former government officials, demurred this week when asked whether the mailed explosives had prompted them to review security measures. Firms appeared to be concerned that commenting on the issue could make them potential targets for would-be attackers.

On Friday afternoon, FBI Director Chris Wray said at a press conference that more packages may still be in transit and urged the public to remain vigilant.