FBI agents arrested an Akron, Ohio man Thursday, accusing him of using social media to encourage attacks on members of the US military.
Terrence J. McNeil, 25, is charged with soliciting others to commit violent crimes. No terrorism charges were filed.
Prosecutors say he used his Tumblr account in September to re-post material from the ISIS terror group, also known as ISIL. It included several dozen photographs, names, and addresses of purported members of the U.S. military.
The ISIS message ended: "Kill them wherever you find them."
McNeil appeared briefly in federal court, where a judge formally advised him of the charges and ordered him held until a detention hearing next week.
A lawyer appointed to represent him had no comment.
Court documents said he declared his support for ISIS in June but had expressed his hopes for violence in the U.S. for well over a year.
Investigators said he used the name "Terrence Broadway" on Facebook in May 2014 and wrote, "I can't wait for another 9/11, Boston bombing, or Sandy Hook," referring to the deadly 2012 school shooting in Connecticut.
A few days later, he posted, "Somebody should park a car bomb in front of a church, school, or mall," prosecutors said.
"Terrence McNeil solicited the murder of members of our military by disseminating ISIL's violent rhetoric, circulating detailed US military personnel information, and explicitly calling for the killing of American service members in their homes and communities," said John Carlin, assistant attorney general in charge of the Justice Department's National Security Division.
A Justice Department official said government lawyers concluded that the social media postings about military personnel were not protected as free speech, because they constituted an incitement to violence.
No information was available on the number of followers of McNeil's Tumblr account, and there was no indication than anyone took any action based on his posting.