This morning when I was walking home from jogging, 
a dog ran at me then jumped on me and tried to grab my bottled water out of my hand.

Do dogs normally do that? 

I don't think they do, but a moment later the dog's owner came running after him and yelled,

Rocky! Leave her alone! That's her bottled water!

When I was a kid I had a dog named Snowball and she would have NEVER ran and jumped on people and tried to grab drinks out of their hand. Why?
Because:
a) I always walked her with a leash
and
b) SNOWBALL HAD CLASS!