Well, two bangs – the twin sonic booms from Endeavour’s hull as it came in to land – and a flash from a fire in an Auxiliary Power Unit exhaust. The shuttle has three APUs used to control hydraulics during powered ascent, reentry and landing, but they can function fine with just one running. The APUs pump and ignite hydrazine to provide energy boosts and that stuttering roaring sound that accompanies the shuttle coming down. On rare occasions, the atmospheric conditions are such that the exhaust is visible as a yellow flame. This has been observed before. Here’s a video of the STS-130 landing from NASA’s Youtube Channel:
The most famous case of an actual APU fire was the ill fated shuttle Columbia that made a perfect landing following STS-9. STS-9 deployed the European in space experiment pallet, SpaceLab 1 back in 1983. It came back to Earth after a computer problem or two and when the orbiter was examined post launch, it was discovered a hydrazine fire had occurred and burnt itself out following a leak in two APUs, creating quite a bit of damage. Nothing was apparent so far as views of the landing from the outside were concerned as you can see from ABC’s coverage at the time:
But there were some actual fireworks as Endeavour went down. As with everything that enters the atmosphere, the shuttle heated up. Looking down from the International Space Station, JAXA‘s ISS expedition 22/23 astronaut Soichi Noguchi tweeted an image he took of reentry.