Sounds very likely to me.
The impact and subsequent secondary effects could easily have heated the atmosphere to 100C and caused massive fires all over. That would do the following:
1. Kill off any land creature that could not find shelter. It is easier for a mouse-sized mammal than a 1/10 to 10 tonne dinosaur to hide in a hole.
2. Warm the surface waters of the ocean sufficient to kill off many planktonic species.
3. Kill every surface plant, but not their seeds.
4. Fill the air with smoke and fumes.