We're still not really sure what killed the dinosaurs.
I mean that both in general and specifically. Yes, there was an asteroid impact. We know that 66 million years ago, an object roughly 10 kilometers across, either an asteroid or a comet, slammed into what is now the Gulf of Mexico just off the coast of Yucatan. The crater is something like 150 kilometers across and 20 deep, and the impact was so catastrophic that 75% of all species died out, including the non-avian dinosaurs. This is called the Cretaceous-Paleogenic, or K-Pg, extinction.