Excuse us.

I went to baseball stadium yesterday. There was so crowd. And then I heard "Excuse us." behind me. 

So, they were two people. I first understood "Excuse us." I always said "Excuse me."

But if we were group, we can say "Excuse us."

I went to the baseball stadium yesterday.
It was very crowded.
While I was standing, I heard "Excuse us." from behind me.
Apparently, there were two people behind me.
It was the first time I heard this word used.
If you are in a group of people, I can say "Excuse us"