A Coon Rapids man has admitted making violent threats against a U.S. senator and could be sentenced to more than two years in prison.

Brendon Michael Daugherty, 35, pleaded guilty Tuesday in U.S. District Court in Minneapolis to interstate transmission of a threat to injure in connection with telephone messages he left with a senator's field office in June.

Public court records do not identify the target of Daugherty's threats other than to say the senator is not from Minnesota.

The agreement between the defense and federal prosecutors includes dismissal of the charge of threatening to murder a United States official.

Daugherty remains in federal custody without bail in the Sherburne County jail.

Federal sentencing guidelines recommend that Daugherty receive a prison term ranging from 15 to 27 months, depending on the impact of his sometimes-violent criminal history. However, federal judges have full discretion when sentencing defendants and are not bound by the guidelines calculation.

Daugherty's plea comes days after a man broke into Democratic House Speaker Nancy Pelosi's home in San Francisco, beat her husband and sought to kidnap her as part of what he told police was a "suicide mission" to target other California and federal politicians, according to a Tuesday court filing.

Paul Pelosi, 82, was knocked unconscious by the hammer attack from David DePape and woke up in a pool of his own blood, the filing said.

Also Tuesday, U.S. Capitol Police Chief Tom Manger provided a sobering update of security protocols for members of Congress. Manger said that although many improvements have been made since the Capitol attack, including the hiring of nearly 280 officers by the end of this year, "there is still a lot of work to do."

According to the indictment against Daugherty:

On June 11, Daugherty left two voice-mail messages on the field office telephone of the senator. In the first, Daugherty said, "You and the Republican Party should be proud that you're pushing me to become a domestic terrorist. Have a nice [expletive] day. Can't wait to kill ya."

In the second message, he said, "I also just wanted to note, thank god the Republican Party is against gun control laws, because it would keep guns out of the hands of a person that was disabled and volatile like I am, but you guys are totally against that. So I may actually get to carry out my nefarious goals."

Field office staff retrieved and recorded the messages and reported them to U.S. Capitol Police.

On Sept. 2, FBI agents spoke to Daugherty at his home. He told them he made the calls because the senator was "doing a bunch of stupid [expletive] with gun control" and that he wants politicians to "feel a little bit pressured."

Daugherty's criminal history prior to the threatening calls could weigh heavily on what sentence he receives.

Court records show he was convicted in October 2018 of two felony counts for threatening on successive days in April to burn down a Pearle Vision store in Maple Grove and harm the employees. Daugherty was angry, according to the charges, over owing $80 for replacement eyeglasses.

His criminal history also includes two convictions for theft and one each for aggravated robbery, burglary, property damage, credit card fraud and fifth-degree assault.

The Associated Press contributed to this report.