In 2019, Lt. Thomas Ahern, a member of the Cambridge SWAT team, experienced an accidental discharge of his Sig Sauer P320 firearm while inside a van during the annual Mayfair celebration. Ahern had previously raised concerns about the safety of the P320 model, alleging it was prone to accidental discharge. Following the incident, Ahern claimed he faced retaliation from the department, including being passed over for promotions. He filed a lawsuit against the City of Cambridge and Sig Sauer, alleging that his whistleblower activities led to adverse employment actions. A federal judge allowed the lawsuit to proceed, recognizing potential First Amendment and whistleblower protections.