A gunshot was fired this morning near the finish line of the Boston Marathon as police responded to a “vicious dog,” prompting a flurry of activity, according to police.

The shot rang out during installation of the finish line markings on the Boylston Street pavement in Copley Square.

As workers were preparing to lay the decal, a Boston Police vehicle when flying down the street and other officers in the area were seen reaching for their guns. Then at 9:22 a.m. a shot was fired, making the police activity more hectic.

But the incident turned out to be a response to a “vicious dog” according to BPD spokesman Mark Marron. The gunshot was either to scare the dog or missed because the animal which was then chased toward the Boston Common where police officers tased and contained it.

Marron did not have the status of the dog when reached at 10 a.m.

This is a developing story.