A 52-year-old man faces up to five years in prison after he admitted last week that he left a vulgar, threatening voicemails for U.S. Sen. Cory Booker at his New Jersey office.

Rick Lynn Simmons, 52, of Kentwood, Michigan, pleaded guilty to one count of interstate communication with threat to injure, the U.S. Attorney’s Office for Western Michigan said in a statement. Simmons, who will be sentenced June 5, also faces three years of supervised release and fine of up to $250,000.

Simmons placed the calls from a cell phone to Booker’s Camden office from his Kent County, Michigan home on Oct. 26.

On multiple occasions, Simmons referenced putting a 9mm gun in the face of the senator, authorities said. Simmons also used several racial slurs in the message.

“I’m just doin’ my guns a blazin’ pal. I got a nine millimeter I’ll put in your (expletive) face, you (expletive). You wanna, you wanna challenge me?,” Simmons said, according to a copy of the indictment.

Later Simmons said, “Come on, you bring it on buddy. Just me and my wife and we got guns a blazin’ you wanna come in here?”

“No individual, whether a public official or a member of the public, deserves to field threatening messages designed to dehumanize, intimidate and terrorize,” U.S. Attorney for Western Michigan Andrew B. Birge said in announcing the conviction.

Booker, who announced last month he’s running for president in 2020, has been the target of other threats in past 13 months. Around the time of the voicemail threat, an explosive “pipe-bomb” style device similar to those targeting Democratic politicians and activists critical of President Trump was addressed to Booker’s Camden office. The package containing the explosive device was intercepted at a South Florida U.S. Postal Service center mail sorting facility in Opa-locka.

A 56-year-old Florida man with a long criminal history was later charged in the nationwide mail-bomb scare targeting prominent Democrats.

Late in 2017, Newark police deployed extra security to protect Booker in response to a death threat against the city’s former mayor. Police didn’t detail the nature of the threat. Booker has served in the U.S. Senate since Oct. 31, 2013. He became mayor of Newark in 2006.