WASHINGTON  The FBI arrested a Washington state man Tuesday on charges he threatened to kill Sen. Patty Murray , D-Wash., over her vote for President Obama's health care initiative.

It was the second time since the bill passed that federal agents have apprehended a suspect for alleged death threats against a member of Congress.

In an affidavit filed in federal court, FBI agents said Charles Alan Wilson of Selah, Wash., threatened Murray's life in a series of obscenity-laced messages left on her office voice mail from March 22 to April 4. The House passed the Senate health care bill March 21, and Obama signed it March 23.

"I hope you realize there's a target on your back now. There are many people out there that want you dead," one message said. "Now that you've passed your health care bill let the violence begin."

Another message included this threat: "I want to (expletive) kill you."

The FBI's affidavit said Wilson, 63, had a permit to carry a concealed weapon and had a .38-caliber Smith & Wesson revolver registered to his name. He had made harassing calls for "several months," but they escalated into death threats after the bill was passed, the affidavit said.

In a statement issued late yesterday, Murray's spokesman, Matt McAlvanah, said the senator's office contacted the FBI at the urging of Capitol Police after receiving "numerous" threatening phone messages. McAlvanah said Murray would have no further comment on the ongoing investigation, but he told USA TODAY that the senator was continuing her public schedule. She spent Tuesday meeting constituents about worker training issues.

The senator, running for her fourth term this year, is a member of the Democratic leadership team in the Senate.

Last week, the FBI announced the arrest of a man charged with threatening to kill Rep. Eric Cantor of Virginia, the second-ranking House Republican leader. The suspect in that case, Norman Leboon, 38, of Philadelphia, was found not competent to stand trial at a hearing Tuesday.

Patricia Hartman, a spokeswoman for the U.S. attorney's office in Philadelphia, said Leboon remains in custody and will undergo court-ordered psychiatric testing.