Partnership deed deceased partner

Mr x and y are in a business M/s shopping complex with 50 :50 partners they collect rent from the firm. In 2007 Y died. mr z is the legal heir for the share they drafted a new deed with z and x as equal partners. but mr x refused to sign. But in income tax returns of the firm of 2008 50 share is shown as transferred to mr z but currently mr x is taking full rent. Please advise what actions can we take and what documents will be required.