I would encourage people to read this article. The visual they portray of the event is incredible.

Edit: Adding the portion from the article that blew my mind

The observation suggests the asteroid is over a kilometer in diameter and the original orbit about the Sun was an Aten type, a class of asteroid that orbit close to the earth, that is resonant with the Earth’s orbit.

This trajectory explains why there is no crater at Köfels. The incoming angle was very low (six degrees) and means the asteroid clipped a mountain called Gamskogel above the town of Längenfeld, 11 kilometers from Köfels, and this caused the asteroid to explode before it reached its final impact point. As it traveled down the valley it became a fireball, around five kilometers in diameter (the size of the landslide).