As the trial of the mass killer at the Tree of Life progressed over the summer, another man was blanketing Pittsburgh with hate and threats. He placed Nazi-themed stickers on street signs and playground equipment around the city, and his haste-filled screeds arrived in the email inboxes of local reporters and Jewish organizations. Photos of people who had testified at the trial, including those who had been wounded in the synagogue attack, showed up on an “enemies list” on his website.

On social media, he pledged to track down the jurors at the trial, sought guidance on making ghost guns and pipe bombs, and urged anyone reading his website to follow the example of Robert Bowers, the man who had carried out the synagogue massacre.

A week after Bowers was sentenced to death, federal agents arrested Hardy Carroll Lloyd in Follansbee, WV, a city about 40 miles from the federal courthouse in Pittsburgh. He is charged with three federal criminal counts, including witness tampering and obstruction of justice in connection with a campaign of threats against people involved in the trial.

For much of the last 15 years, Mr. Lloyd was in and out of prison, serving a sentence on gun convictions, authorities said. Multiple times, he was let out, only to be sent back for violating the terms of his release, including urging violence against Jews.

He is to remain in custody pending a hearing and further legal action.                         Getty Images