Yonkers police have joined the NYPD and its internal affairs division to see whether an off-duty New York City cop was responsible for a brutal assault outside a Yonkers bar.According to police, a fight broke out September 14 on McLean Avenue. A 26-year-old Yonkers man was severely beaten and had to be rushed to the hospital for emergency surgery. Police say the victim may lose an eye as a result of the attack. NYPD officers who were the first to respond to the incident and witnesses have reported that New York City police detained and then released someone before Yonkers police arrived at the scene. Yonkers Police Commissioner Edmund Hartnett says whoever is responsible will be charged with felony assault once that person is apprehended. Anyone with information is asked to contact the Yonkers Police Department at 914-377-7725.