(CNN)An Iowa man has been arrested by federal agents after he threatened to kill Jews in hate-filled phone calls and emails, according to court documents.
Garrett Kelsey, 31, admitted in a voluntary interview to calling and emailing a Jewish organization with messages full of anti-Semitic and racist language, the documents said. He was arraigned on Tuesday in a federal court in Iowa on charges of making interstate threats.
Kelsey was apparently upset about a video regarding Nordic neo-Nazis that the group had posted, the affidavit said.
"My people have f***ing slaughtered your f***ing people before and we will do it again. And right now, you are giving us incentive to do that. ... Filthy f***ing Jews," Kelsey said in a message to a Jewish organization based in New York, according to court documents.
Kelsey's profanity-laced email to an employee warned the group had three days to remove the video or "we will be taking action against your organization full of degenerates," the affidavit said. The Cedar Rapids resident also wrote that "everywhere Jews go in the world they cause trouble."
A Special Agent with the Joint Terrorism Task Force of the FBI who helped investigate the case detailed in the affidavit Kelsey's social media trail, which includes blatant use of anti-Semitic and racist language and Neo-Nazi tropes.
A week after the voluntary interview with authorities, the agent says Kelsey changed his now-deleted Facebook cover photo to one that depicts people lined up facing a wall with their hands up, according to the agent. The photo shows Jewish residents in a Warsaw, Poland, ghetto before being transferred to concentration camps, according to the agent.
Kelsey used the Facebook account to leave a message on the page of the group "Iowa Antifa" in which he threatened that, if he saw any of them, he would "bash your skulls in without warning!" according to court documents.
He then wrote "white is might!! 1488!!" according to court documents. 1488 is a Neo-Nazi reference: the 14 refers to the "14 Words" of a popular white supremacist slogan, and "88" refers to "Heil Hitler" (H is the 8th letter in the alphabet).
Kelsey was arrested and arraigned in Iowa and is scheduled to be in court for another hearing on Thursday, his public defender Christopher J. Nathan told CNN. Nathan would not comment further on the case. The case is expected to be transferred to New York for prosecution, according to prosecutors in Iowa.
Manhattan US Attorney Geoffrey S. Berman said in a statement that the profanity-laced threats are "not protected speech."
FBI Assistant Director William F. Sweeney Jr. appeared to agree.
"The FBI will always follow threats that cross the line of free speech and threaten the safety of individuals and groups, especially when those threats are based on a religion or race," Sweeney Jr. said in a statement. "The fact that Mr. Kelsey allegedly continued his threatening behavior even after being informed that his previous actions were not protected speech makes his actions more abhorrent."