Clinton, Westbrook, Essex and Guilford fire departments were also all on scene.
The call came in just after 4 p.m. and the fire was under control as of 5 p.m., with remaining crews putting out some hot spots.
The front part of the building is a single-family house with an annexed attic apartment. Nobody was inside the apartment at the time of the fire.
The fire started on the first floor at the back of the home, and started traveling across the attic space, but there was no word on what caused the fire.
Flames were contained to the back of the home and the attic, but there was no No damage to the gun store section of the structure
The firearms store didn't sustain any damage and had actually closed a few months ago, but there was ammunition inventory remaining in the store that had fire officials concerned.
"The ammunition is flammable," said Joe Johnson, Old Saybrook deputy fire chief. "So if it heats up it will start going off. The rounds will start shooting off. We didn't have any shoot-off. We were able to stop the flames from getting to that section of the business."
The Old Saybrook Fire Marshal's Office and the Old Saybrook Police Department have ruled the fire accidental and not suspicious.
