Police told CNN state troopers responded to a call to Paul's residence at 3:21 p.m. Friday.
Boucher lives on Rivergreen Lane, inside a gated community in Bowling Green, according to the Warren County property valuation administrator's website.
A spokesperson for Paul confirmed the senator suffered five broken ribs in the incident.
His communications director released a statement, saying the senator was "blind-sided" by his attacker.
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"Kelley and I appreciate the overwhelming support after Friday's unfortunate event", Paul tweeted. According to the release, Boucher was arrested by Trooper Bartley Weaver and charged with assaulting Paul, a Republican who has been Kentucky's junior senator since 2011. "Thank you for your thoughts and prayers".
While a motive is not officially known, Jeff Jones, a registered nurse who worked with Boucher at the Bowling Green Medical Center, described Boucher's politics as "liberal". Paul was mowing his lawn at the time of the attack, television station WAVE-TV in Kentucky reported.
CNN was unable to reach a representative of Boucher on Saturday night.
Hodges said Boucher would have faced more serious charges if had he used a weapon or if Paul had been injured seriously.
The investigation is ongoing.