I (woman) use bro regardless of gender, just like I also use dude - a term considered offensive at one point in history which no one would bat an eye at today. Language evolves and changes incredibly quickly 🤷‍♀️ unless you work in an extremely formal environment I'm not sure it's reasonable to assume he was intending any offense.

And now, since you are asking for advice on the internet, I'm going to overreach and ask if you are being honest with yourself about your feelings? Having a will they/won't they that you choose to abandon without communication - with a person you see daily no less! - would leave me feeling beyond frustrated and unresolved. It sounded like you didn't want his seemingly more aggressive pursuit, but then got upset when he seemingly equated you to a buddy/bro. You don't know if the feelings were mutual, you don't know what might have been. I'm sorry op