Why would firefighters be walking around on top of the roof of the grocery store across the street from my apartment?

(This event is currently unfolding.) Moments ago, two firetrucks and an ambulance arrived in the parking lot of the shopping center across the street from my apartment. A few firefighters entered the building at ground level with hatchets, and then one of the trucks extended the ladder so four firefighters could use it to go up on the roof of the building.

None of them seem to be hustling, and I can’t smell any smoke.

Any idea what could be going on over there?