Accepted offer then realtor presented another offer

[Kaylyn T.]

Hi BP, I'm reaching out hoping someone can shed some light on a sticky situation I have right now on a property I'm negotiation in Maine. It's after 10 east coast time or I would call my attorney, so hoping someone can give me some advice here until Monday. 

I presented and offer of 150k on a property in writing through my realtor. The sellers realtor countered with 165k final via verbal communication to my realtor. I accepted. She called him to tell him this. He then tells her, write it up because I'm out of the office. She does. I sign it. She emails it to him and follows up with a call. He then tells her - not 10 minutes after the previous call with the final accepted offer call - that he got a call that another offer was going to be presented. My Realtor asks that he present our acceptance. He does not. He waits on the other offer. It is higher, so now I am in a multiple offer situation. 

So obviously the question is - Is this legal? And is there anything I can do about it? 

Really appreciate any advice. 

Thank you!