Paul K. Curtis, 45, who has worked as an Elvis impersonator, was arrested Wednesday as a suspect in the mailing of the suspicious letters to Obama and U.S. Sen. Roger Wicker, R-Miss.
Wicker said Thursday he had once hired Curtis to perform as The King at a party, NBC News reported.
"I have indeed met him," Wicker said. "He was very entertaining."
"He was more stable then," Wicker said.
An FBI bulletin obtained by NBC News Wednesday indicated both letters contained identical statements.
The letters, which bore a Memphis postmark of April 8, ended with the phrase, "to see a wrong and not expose it, is to become a silent partner to its continuance." The letters also signed off with: "I am KC and I approve this message."
Curtis was arrested at his Corinth home Wednesday following an investigation involving federal, state, and local law enforcement.
The suspicious letter addressed to President Obama was flagged at an off-site White House mail-processing facility. The suspicious letter to Wicker also was flagged at another off-site facility.
Sheriff Jim Johnson of Lee County, Miss., said a letter received by a Mississippi judge April 10 included "wording that was of interest" as well as some "suspicious content." It, too, was postmarked from Memphis, NBC News said.
Suspicious envelopes were hand-delivered to the Capitol Hill offices of senators from Alabama and West Virginia, prompting evacuations of their staffs, and lockdowns of many more Wednesday.
Also Wednesday, the bomb squad was called and Senate employees were told not to leave their offices after a bag was discovered at the entrance of a Senate building, the Post said. After two hours, the package was cleared, as were two letters delivered to the offices of Sens. Joe Manchin III, D-W.Va., and Richard C. Shelby, R-Ala.
In Phoenix, a suspicious letter was discovered Wednesday at the office of Sen. Jeff Flake, R-Ariz. Flake later said in a statement tests were negative for ricin.
Sen. Carl Levin, D-Mich., said in a statement an employee got "a suspicious-looking letter" Wednesday at the senator's office in Saginaw. The letter was being investigated, he said.