Recently, and by accident, I learned on the Internet that my mother passed away. My estranged sister had put my mother in a nursingdid not notified me

My widowed mother past away a couple of months ago. She did not have property to her name in NY (She was retired resident of NYC) or any other state in the US, however I believe she did have a bank account/s. I am not sure if she left a will or not. How to I find out the if she left a will, and what to do next. Also if there is no will how to I find out the existence of any assets such as bank accounts etc. Who to contact? What to do first. Mother was very secretive her entire life. My sister knows more however she is not willing to communicate any information. No other siblings alive.