Well that depends. Was there a specific task to be completed before you arrived, that was your job to do? If so, even if you were the first one but were late for said task, it is definitely a reason to be yelled at.

Well that depends. Was there a specific task to be completed before you arrived, that was your job to do? If so, even if you were the first one but were late for said task, it is definitely a reason to be yelled at.

if you were supposed to open up? be there to answer the phone? etc

No, you were not the first, your boss was. Your coworkers could of gotten the same treatment, it's just you were the "first" to get it.

tell them you do what you want and to shut their mouth bosses like it when your assertive !!!!

Seriously need a follow up on this one. Because I am not following your boss's logic.

Late is late, you were just the first so you got yelled at first. I see nothing wrong here