Updated: 2:04 p.m. ET
(CBS News) -- Democratic Missouri Senator Claire McCaskill, who is in the midst of a tough re-election fight, will receive increased security protection following a recent threat to her safety, St. Louis County Prosecuting Attorney Bob McCullough confirmed to CBS News Wednesday.
McCaskill was threatened by a conservative activist named Scott Boston at a Tea Party event last week, according to the St. Louis Post-Dispatch, which first reported the story. Boston told the crowd "we have to get Claire McCaskill out."
"We have to kill the Claire Bear, ladies and gentlemen," he said. "She walks around like she's some sort of Rainbow Brite Care Bear or something, but really she's an evil monster."
You can hear audio of the comment in a video captured by American Bridge, a Democratic super PAC.
McCullough said the Kirkwood Police Department has enacted "enhanced" security in the area where McCaskill lives.
Boston later walked the comments back, arguing that he had meant the statement metaphorically.
Still, the incident prompted the U.S. Capitol Police to contact the Kirkwood Police Department and McCullough's office, which led to the increased measures.
Sarah Steelman, a Republican Tea Party candidate vying for McCaskill's Senate seat, was at the event at which Boston made his initial comments, and came to his defense on Tuesday in a statement.
"When a conservative citizen makes a statement, the liberal press attacks it and spins it in the worst way," Steelman said. "Yet when President Obama states: 'If they bring a knife to the fight, we bring a gun', or his Senator, Claire McCaskill, suggests: 'We should take up pitch forks if Congress doesn't raise taxes', the liberal media applauds it."
Steelman noted that "I may disagree with the words Mr. Boston chose in his statement," but she sympathized with his "frustration."
"This is a typical double standard and why we conservatives are at war with the liberal establishment," Steelman said. "I may disagree with the words Mr. Boston chose in his statement, but I understand his frustration and I emphatically support his right to express his views."
Sen. McCaskill's office declined to comment on the matter. A spokesperson for the U.S. Capitol Police said in an email that the department does not discuss the security of Congress members but that the USCP "currently has an open and active investigation and is working with local law enforcement."