A man is facing a serious charge after deputies say he threatened Congressman Brian Mast's children.

A federal document filed with the U.S. District Court states Laurence Wayne Key called Rep. Mast's office in Washington, D.C. on Monday morning. An intern told investigators when he answered the phone the caller said, "I'm going to find congressman's kids and kill them. If you're going to separate kids at the border, I'm going to kill his kids. Don't try to find me because you won't." Investigators found the phone number belonged to Key, who lives in Stuart.

Documents claim Key has called Mast's office 478 times and also contacted Senators Marco Rubio and Bill Nelson.

According to the complaint, during an interview with an FBI investigator, Key denied threatening to kill Mast's children, but admitted he said Rep. Mast should be separated from his kids.

Key is charged with threatening to kidnap or injure a person.