An Omaha man has been arrested by the FBI on suspicion of making threats against Republican U.S. Sen. Joni Ernst of Iowa, including that he "could kill" her.

Federal court records show Robert William Simet, 64, was arrested Friday in Omaha and charged with threatening a U.S. official.

"The safety of our elected officials is something that cannot be taken lightly," FBI Omaha Special Agent in Charge Randall Thysse said in a statement. "We appreciate those people who reported this to the proper authorities and for the response from our partners at the U.S. Attorney's Office for the Southern District of Iowa for their swift action on this matter."

An arrest affidavit says employees of a Pacific Junction, Iowa, motorcycle shop told an FBI agent that Simet had been there Wednesday and made several statements about Ernst, including his belief that she was a member of the Islamic State.

Simet said he knew Ernst was scheduled to speak Saturday at an event at the motorcycle business. Simet is accused of telling an employee he "could kill" Ernst at the event, and told another employee that "everyone in the government needs to be killed off."

Simet is in custody and will be transported to Council Bluffs for an initial appearance in the Southern District of Iowa on Tuesday.

Ernst's office referred questions to U.S. Capitol Police, which said Friday it does not comment on ongoing investigations.

The Associated Press contributed to this report.