First I would see if there is an estate for this individual. Check with the Surrgogate's Court, I think the probate court is called that in New York. See if there is a file for the deceased owner. If not, you could try to see what his/her death certificate says as far as survivors. I assume you have reviwed the deed to make sure who the legal owner was.
I suggest that you first find out who owned the property on ACRIS. Then contact the Public Administrator of Kings County to see if they are handling the estate.
Merely because a property is vacant does not necessarily mean the owner is dead or even that there is no owner.
(You aren't talking about the place opposite Two Boots, are you?)
Go to the website of the NYC Department of Finance at the link below. Then find out the BLOCK and LOT number corresponding to the address. Then, click on the second like below and find out if anyone is paying the Real Estate Taxes on the property.
If there is someone paying those taxes, contact him and find out if he is in a position to help you.