Claims against a dead person.

My son expired while in sleep. He left no account of his money dealings. his business was of fabrication. He left no clue/Diary or any document in respect of his financial transaction. Now the lenders are appearing with blank Cheques, copies of property paper incl. Agriculture Land. not in the name of deceased. none is coming who owe to him. How these person can claim against the property papers in their possession. I am also a lawyer joined this profession after my retirement. Can we debate on these issues?