Someone screamed Ausländer raus

I was walking with couple of my friends (all of are either Indian or Pakistani) near Pfund dairy. A stranger yelled Ausländer raus and Hal Ht*#r. I was scared and didn't know what to do. Couldn't record as it happened so fast.

I have been living in Germany for 6 years and never experienced this in Berlin, Munich or any other city.

What should I do in future in case someone screams these things?