PIERRE, S.D. (AP) — A South Dakota man accused of threatening U.S. Sen. Tim Johnson because the senator allegedly supports gun control has been taken into custody.

Jonathan Constantine, of Piedmont, has been charged in federal court with transmitting in interstate commerce a threat to injure another. A conviction on that charge carries a maximum penalty of five years in prison.

Constantine allegedly posted a threatening message March 16 on the Democratic senator’s Facebook page. An affidavit by an FBI special agent from Rapid City said Constantine wrote: “I’m giving you a last warning tim. Stop supporting gun control. It will be the last thing you ever do. If you want to end up dead somewhere just keep supporting it.”

According to the affidavit filed in federal court, Constantine showed up at the senator’s Rapid City office April 11 and screamed at the staff regarding Johnson’s alleged support for gun control measures in Congress. 

The FBI agent’s affidavit said Constantine said he would not talk to agents without a lawyer present, but Constantine then added: “But I will say this about it, it was not a threat.”

Constantine made his initial court appearance Monday by video conference with a federal judge based in Sioux Falls. An assistant U.S. attorney from Iowa handled the hearing for the prosecution because U.S. Attorney for South Dakota Brendan Johnson is the senator’s son. 

Neil Fulton, federal public defender for South Dakota and North Dakota, said his office was still studying the allegations.

“As with anyone, when you’re indicted you’re simply charged. It’s an allegation. It’s not proof of anything,” Fulton told The Associated Press.