Steps to follow for the rights in the intestate property

I know a family where father and mother both worked very hard for 30 years and bought two adjacent flats in Mumbai city. They had a Son and three daughters, all three daughters are married and well settled. Son is into Real Estate business. Both the parents died without leaving any Will. They were practicing Sunni Muslims. The two flats is occupied by the Son and his family now. The question is now the son wish to pay certain amount to all three sisters and wish to transfer these two flats in his name. What is required to be done in this case ? Whether the property of the deceased parents needs to be transferred in the name of the legal heir ( Son and three daughters) first or the son can inherit the property in his name, by paying the agreed sum to the sisters , directly. What documents need to be executed ? What will be the share of the son and three daughters each.? All the answers be in the light of Muslim personal Law.