A Shot in the Middle of the Night

Early this morning, the Mr. and I were awoken by a flash and then the cracking sound of a shotgun outside our window.
It was a great storm, the kind with lightning so bright you think hundreds of people are shining flashlights into your house, and the thunder has the initial dry bang of an old school gun.

The first few lightning bolts were very close to our place--the thunder chimed in just on the tail end of the lightning.  We laid in bed, looking at each other, and going "WOOOOOAH!!"
We don't get storms like this in Utah.
It reminded me of a good South Dakota thunder storm, only the apartment wasn't shaking like the booming thunder tends to make buildings do in the big SD.

He had to get up and close the window because the rain came pouring in.

Unfortunately (or maybe, for the best, since you just can't sleep through that kind of storm), it was fast-moving and we only had intense thunder and lightning for 5 minutes, then heard it fade away into the distance as it moved toward the mountains.

As I drifted back to sleep, I wondered why people call it "lightning AND thunder,"
 as if the thunder is its own entity, and not a sound created by lightning.