Senate Sergeant at Arms Terry Gainer said there was no current threat to the lawmaker, who has been notified of the development, but Capitol Police were keeping apprised of developments from both state and local law enforcement agencies, The Hill reported Thursday.
During a briefing Thursday FBI Deputy Special Agent in Charge Joe Persichini said a search of suspect James W. von Brunn's car turned up "documents and papers" containing names and addresses. Officials made contact "if there was any type of potential threat."
Von Brunn was listed in critical condition at a Washington hospital from a gunshot wound he received during an exchange of gunfire with Holocaust Museum security guards Wednesday. The suspect was charged with murder in the shooting death of security guard Stephen Tyrone Johns, 36.
The criminal complaint filed with the U.S. District Court for the District of Columbia said a notepad found in von Brunn's car contained a notation from the suspect that President Barack Obama was "created by Jews" and stated his concern that he would have his weapons taken away, the Washington publication reported.
The complaint, quoting von Brunn's notebook, said: "You want my weapons -- this is how you'll get them. The Holocaust is a lie. Obama was created by Jews. Obama does what his Jew owners tell him to do."
FBI officials are looking into possibly filing charges of civil rights violations and hate crimes, said Persichini of the Washington FBI field office.
"We know what Mr. von Brunn did yesterday at the museum. Now our responsibility is to determine why he did it," Persichini said.
The FBI had no active investigation on von Brunn but knows about him and his anti-Semitic views, activities and publications, including a Web site, Persichini said.
Washington Police Chief Cathy Lanier said "a caring" Johns opened the door to allow von Brunn to enter the Holocaust Museum. As he entered the foyer, von Brunn raised his rifle and opened fire, striking Johns before being shot by two other security guards.
The Holocaust Museum was closed Thursday and flags flew at half-staff to honor Johns.
Notable deaths of 2014 [PHOTOS]