Wow! Even very simple critical thinking could ferret out the lie here.
How would the fire department know there was a gas leak in the building unless they were on the scene?
If they were on the scene they would use fans to ventilate the building and direct the evacuation and ensure that it was complete.
The fire departments mission is to prevent or minimize the destruction of property not to direct its destruction.
This Battalion Chief Bubba, is this the Manager? OK, we've automatically detected a gas leak from interior gas alarm sensors. You better smash all the windows before the place blows. We're responding to the scene code 3 now.
Yes... the first safety step if there IS a leak is GET OUTTA THERE...