(CNN) -- Police arrested a 64-year-old Washington state resident who authorities say made death threats against Democratic Sen. Patty Murray of Washington, the Justice Department announced Tuesday.

A department statement said the suspect, identified as Charles Alan Wilson of Selah, Washington, made the threats in phone messages to Murray's office between March 22 and April 4.

Wilson allegedly stated that Murray "had a target on her back" and that he wanted to kill her, according to the statement, which said the threats were in response to congressional passage of the new health care bill.

According to the statement, Wilson allegedly "told undercover FBI agents that he regularly carries a firearm with a concealed weapons permit" and "also stated that he was extremely angry about the passage of the health care reform legislation."

A statement from Murray's office said that after receiving the phone calls, staff contacted the Capitol Police Department, which advised them to contact the FBI. The office declined to comment further, citing the ongoing investigation.

"Senator Murray will continue to focus on working for the people of Washington state," the statement said.

Threatening a federal official is punishable by up to 10 years in prison and a $250,000 fine, the Justice Department statement said.

Threats against U.S. senators and representatives increased as Congress held its final debates and votes on the health care bill, which was unanimously opposed by Republicans. In addition, conservative activists around the country protested the bill.

Most of the reported threats were against Democrats, though there were some against Republicans.