Hi Vineet,
As far as the policy part is concerned, if you don't have any clause in relation to termination during probation period then you can review past practices of ur org. in this regard...or simply go ahead with firing the person. However, it wud be unethical & certainly not an hr's approach to tackle such matters. Rather, instead of jumping to conclusions, try to find out the actual reasons responsible for his poor performance...have a one-on-one discussion with the employee in question & lend out a helping hand to sort out his problems. Look at this issue from different perspectives & don't rely on his deptmental f/b alone. Atleast, for initial few months, an employee's performance is a sum total of ...individual caliber, seniors' guidance and work-culture.Consider all these factors & go ahead as deem fit.