Okay so there's this guy?

He works with me and he's really cute and i like him. And i think he may also be interested in me. And last night he kinda jokingly asked me out (like at work was like "Brittany will you go out with me") like in front of everyone i just kinda froze and was like i dont know how to answer that. And i'm really not sure why he said that. He doesn't really date much. However there's a problem he's one of my good friend's ex-boyfriend. And she also works with us. It was like over 6 months ago but she's still like in love with him. And he wants nothing to do with her. So she'd pretty much hate me if anything happened between me and said guy. So i'm kinda wary about advancing this.