Federal authorities patrol outside the federal courthouse in Charleston, S.C., on Nov. 7. (Chuck Burton/AP)

Jury selection was scheduled to begin Monday in the trial of a man charged with killing nine black parishioners at a Charleston church last year, but a federal judge abruptly postponed it without offering much of an explanation.

At the same time, officials in Charleston said they were investigating reports of threatening letters recently sent to locations in the city, one of which referred to the alleged gunman. At least two others went to the church where the massacre occurred. Officials did not say whether there was any connection between the letters and the trial.

Dylann Roof, 22, faces a possible death sentence in the federal trial stemming from the killings at Emanuel AME Church last year. The Justice Department said earlier this year it would seek the death penalty for Roof, a rare punishment for federal prosecutions, after he was charged with federal hate crimes in a 33-count indictment.

The beginning of jury selection Monday was set to start would probably be a months-long trial process, a lengthy and unsettling experience for a community that is also seeing another high-profile case unfold. While Roof’s trial is scheduled to proceed, a former police officer charged with murder for shooting an unarmed black man who was fleeing from a traffic stop is on trial in the same city.

In a written statement, District Judge Richard M. Gergel said that he was canceling the jury selection process planned for Monday after receiving a motion requiring a hearing with only Roof and his attorneys.

Gergel did not elaborate on the motion or the sudden need for the hearing, which was also closed to federal prosecutors.

“The closing of the hearing is necessary to protect the attorney-client privilege and the defendant’s right to a fair and impartial jury and a fair trial,” he said.

An attorney representing Roof filed a sealed motion Sunday, and a pair of sealed documents were filed in the case Monday. After the hearing, court officials said that the jury selection process would reconvene Wednesday morning. Gergel then signed a pair of orders that were sealed from public view.

In addition to the federal case, Roof also faces a possible death sentence in a state trial that is set to begin next year.

Prosecutors have said in court filings that they believe Roof “self-radicalized” online, absorbing violent white-supremacist beliefs from material he found on the Internet.

After the attack, authorities found an online manifesto filled with racist comments that they say belonged to Roof. Prosecutors also say they have located two handwritten manifestos, including one found in Roof’s jail cell.

On Monday, authorities in Charleston also said they were investigating several reports of letters with racist and anti-Semitic threats and comments received in recent weeks.

At least one letter mentioned Roof, according to Charleston police reports released by city officials. Police reports say that these letters arrived at hotels, a county park and the “Mother Emanuel” church.

The Charleston police incident report on the letters sent to the church did not specify details, other than to say they were “two letters from an unknown suspect that were harassing in nature.”

Some of the messages included violent threats aimed at Jewish, black, Muslim and Hispanic people. One appeared to be postmarked from a facility in England, while others appeared to have Canadian postage.

Further reading:

Justice Department will seek death penalty for accused Charleston church gunman Dylann Roof