A "vicious dog" evaded police officers near the Boston Marathon​ finish line on Thursday, prompting an officer to fire their gun.

A Boston police officer opened fire on a dog outside the Boston Public Library on Thursday morning, officials say. At 9:22 a.m., officers responded to a call at the Boston Public Library, located at 700 Boylston St., according to a statement from the Boston Police Department.

One officer fired his service weapon and several Taser rounds were also discharged at the dog which fled from the scene and was later located at Downtown Crossing, police said.