A 39-year-old Massachusetts man has been charged with sending “racist, offensive, and threatening” emails to Philadelphia Police Commissioner Danielle Outlaw earlier this month, federal authorities announced Tuesday.

Peter Fratus, 39, of West Dennis, Mass., sent two emails to Outlaw on June 6 with “vile and disturbing” language, and in one of them, asked where she lived, U.S. Attorney William M. McSwain said.

"We take such threats very seriously, and let this be a warning to anyone who might feel the urge to fire off an online threat directed at a public official: We will trace your digital footprint, track you down and hold you accountable,” McSwain said in a statement.

Outlaw, through a police spokesperson, declined to comment.

According to a criminal complaint, Fratus’ short emails were peppered with racial epithets, and one made a crude reference to the Holocaust.

Fratus made an initial appearance in district court in Massachusetts before he was to be transferred to Pennsylvania, federal officials said.

Outlaw, the first black woman to lead the city’s 6,500-member Police Department, took over in February after Mayor Jim Kenney announced her appointment at the end of last year.

She had been tasked with helping reform a department that faced a series of crises in 2019, including a scandal over hundreds of officers making racist or otherwise offensive Facebook posts, the abrupt resignation of former commissioner Richard Ross over claims in a sexual harassment lawsuit, and stubbornly high levels of gun violence.

Her first four months on the job have presented a series of unexpected challenges, including widespread protests over the police killing of George Floyd in Minneapolis.

Fratus’ emails, sent a week after those demonstrations began, came as the Police Department was thrust into the national spotlight over its response to the unrest, including the use of tear gas in West Philadelphia and on Interstate 676.

Federal prosecutors did not say what may have motivated Fratus to send the emails to Outlaw. In the criminal complaint, they also allege that he left threatening voicemails for a “Massachusetts government official” whom they did not identify.

Prosecutors said Fratus, in an interview with the FBI and Massachusetts State Police, “admitted that he sent the threatening messages” to the unidentified official and to Outlaw, and said he had “crossed the line.”

It was not immediately clear if Fratus had retained an attorney. He faces one count of sending interstate threatening communications, which carries a maximum prison sentence of five years.

Outlaw had previously served as police chief in Portland, Ore., after spending two decades rising through the ranks in her hometown of Oakland, Calif.