Why are my bullies nice to me when their friends ain't around them?

He's not a bully. I bet he's just trying to look cool and then when his friends aren't around his real personality shows. He's a fake though

Typical....you see, they want to look "Cool" In front of their friends...you need to call them out on it. They are not so tough when they are alone....next time say "Gee your personality changed so fast from yesterday, what happened? Are you only mean when you are around your friends?"