What happens if I get a fake $100 dollar bill?

Hello there, I'm curious to know what would happen if I were to come across a fake $100 dollar bill. Would I be held responsible for it? Would there be any legal consequences? I'm also wondering if there are any ways to identify a fake bill to avoid any potential issues. It's important for me to understand the risks and procedures associated with handling such a situation. Could you please elaborate on what steps should be taken if one were to encounter a fake $100 dollar bill? Thank you for your assistance.