Colorado GOP Senate candidate Cory Gardner’s attendance of a fundraising event hosted by a fellow Republican who cast doubt on the Sandy Hook school shooting has provoked some strong responses from those close to the shooting.

Sen. Chris Murphy (D-CT), whose state was devastated by the killing of 20 students and six adults at the elementary school in December 2012, called the reports “sickening.”

Reading reports that @CoryGardner is supporting election of a Sandy Hook “denier” in Colorado. That is sickening. — Chris Murphy (@ChrisMurphyCT) September 12, 2014

Gardner attended an Aug. 23 fundraising event at the home of Tom Ready, the Republican candidate for Pueblo County commissioner. At a debate this week, Ready said of the Sandy Hook shooting: “There is still question whether it really happened.”

In a statement Friday, Jane Dougherty, whose sister Mary Sherlach was a school psychologist killed at Sandy Hook, called Gardner’s association with Ready “appalling” and demanded that Gardner and GOP gubernatorial candidate Bob Beauprez, who was also at the event, disavow Ready’s comments.