U.S. Sen. Susan Collins. Credit: Gabor Degre

A New York man who threatened U.S. Sen. Susan Collins and another Republican senator over their support for Brett Kavanaugh’s nomination to the U.S. Supreme Court was sentenced Monday to 18 months in prison.

Ronald DeRisi, 75, of Smithtown, New York, pleaded guilty in federal court earlier this year to sending numerous threatening voicemails to Collins and Chuck Grassley, a Republican from Iowa who chaired the Senate Judiciary Committee during the Kavanaugh hearings.

Prosecutors had sought a longer sentence for DeRisi, saying he went to great lengths to hide his identity, according to the Associated Press.

[Collins brings in most money of her career after Kavanaugh vote]

“Our political process allows for vigorous debate, but not destruction. Threatening to harm or kill elected officials because one disagrees with their public positions goes far beyond the scope of the First Amendment and will not be tolerated,” Richard Donoghue, the U.S. attorney for the Eastern District of New York, said in a statement Monday. “We will not allow individuals to influence political decision-making through criminal threats.”

DeRisi’s attorneys described the New Yorker as an “angry, sick old man” and said that Kavanaugh’s nomination sparked in him an “inexplicable rage.” But they maintained that DeRisi’s physical condition made it impossible for him to carry out his threats, the Associated Press reports.

In addition to his 18 month sentence, DeRisi will also forfeit ownership of two firearms, Donoghue’s office said.

Prosecutors said that DeRisi began sending threatening messages on Sept. 26, the day before Kavanaugh appeared before the Senate Judiciary Committee to address accusations that he sexually assaulted California professor Christine Blasey Ford in the 1980s when the two were in high school. Kavanaugh denied those accusations.

[Collins says she doesn’t believe Kavanaugh assaulted Ford]

DeRisi left approximately 12 voicemails in which prosecutors said he threatened to assault and kill the two senators. In one of his messages, DeRisi threatened to shoot one of the senators in the head with a 9 mm firearm, according to the U.S. attorney’s office.

He was arrested on Oct. 19, 2018, 13 days after Collins cast a decisive vote to confirm Kavanaugh to the Supreme Court, where he took the seat of retired Justice Anthony Kennedy.

Collins was the target of harsh criticism and attacks during and after the Kavanaugh confirmation. Her offices were targeted with at times threatening voicemails, which Collins called in mid-September 2018 a “new low.”

On Oct. 18, 2018, local, state and federal law enforcement agencies, including a Hazmat team from Orono, investigated Collins’ West Broadway residence in Bangor after a letter that claimed to be contaminated with rici was sent there. Collins was not home at the time. In a separate case, Suzanne E.Muscara, 37, of Burlington has pleaded not guilty to sending a threatening letter to Collins that contained a white powder the sender claimed was anthrax. The letter was intercepted at the U.S. Postal Service’s sorting facility in Hampden.

Related: Police discuss response to suspicious letter to Collins’ Bangor home