A Florida man has pleaded guilty to threatening to kill Alexandria Ocasio-Cortez and Nancy Pelosi, two leading Democrats in Congress, and Kim Foxx, a prominent district attorney in Illinois.

The US attorney’s office for the southern district of Florida said Paul Vernon Hoeffer, 60, entered his plea in federal court in Fort Pierce on Friday.

Hoeffer admitted calling Pelosi’s Washington office in March 2019, threatening “to come a ‘long, long, way’ to rattle her head with bullets and cut her head off”.

He admitted a call to Foxx on the same day, saying bullets would “rattle her brain”.

In November 2020, Hoeffer called the office of Ocasio-Cortez, a leading progressive from New York. This time, the DoJ said, Hoeffer “threatened that he would ‘rip her head off’, and told her to sleep with one eye open”.

Citing the plea agreement, NBC News reported that Hoeffer also “warned of ‘all-out war’ and a ‘civilian army’” and made racist remarks in his call to Foxx.

Hoeffer made his calls before the attack on the US Capitol on January 6 2021, in which supporters of Donald Trump sought to overturn his election defeat.

Some looked for lawmakers to capture or kill. One rioter, from Texas, faces charges including a threat to “assassinate” Ocasio-Cortez. His case has yet to be tried.

Capitol police have reported an increase in threats against lawmakers. NBC cited the chief of Capitol police, J Thomas Manger, as saying there were around 9,600 threats in 2021, up from more than 8,000 in 2020.

As prominent Democratic women, Ocasio-Cortez and Pelosi are common targets for threats, from within the walls of Congress as well as without.

Ocasio-Cortez was elected in 2018, as Democrats took the House in opposition to Trump. She quickly became a national star. In 2019, Time magazine began a profile by describing nerves in her Washington office.

“Every 10 minutes or so,” the magazine said, “someone knocks on the big wooden door of Alexandria Ocasio-Cortez’s office on Capitol Hill. The noise makes staffers stiffen.

“It’s almost always a harmless fan, one of dozens who arrive each day, leaving neon-colored Post-it notes as devotional offerings.

“But in her first three months in Congress, aides say, enough people have threatened to murder Ocasio-Cortez that Capitol police trained her staff to perform risk assessments of her visitors.”

This, the magazine said, was “the daily reality for America’s newest human Rorschach test. Wonder Woman of the left, Wicked Witch of the right”.

At sentencing in April, Hoeffer will face up to 15 years in prison.