If your chimney looks like a roman candle you're having a chimney fire. In this case here it was a creosote fire on the metal cap. Special ladders with roof hooks are used, not particularly scary on this cape cod style house but still dangerous. Inside, firefighters are using a Thermal Imaging Camera (TIC) to look for heat extension behind walls. A good reminder to have your chimney swept.
The firefighter on the roof is one of the top rescue professionals in the nation with a history of mountain rescue, swift water rescue, and hurricane rescue in multiple states. He's also an instructor to major urban departments. Any one of these guys would go head first through a window to save your family.