Out for a walk

So I went out for a walk last night and there was a woman walking ahead of me. She started to walk faster, and I thought if she is walking faster, I should walk faster too.
Then she started to run. I decided that maybe that would be a good idea as well.
Then she started to run even faster, so I ran faster too.
Then she started screaming, so I started screaming.
I have no idea what it was all about, but believe me, I have never been so scared in my life.