VVIP chopper scam: Who took the bribe?

CBI has called for questioning former Air chief S P Tyagi and former deputy Air chief J S Gujral in connection with its probe into the alleged corruption in Rs 3,600 crore AgustaWestland VVIP chopper deal. Now the question is if ED has any knowledge of who is at fault or who is lying then why isn’t it making it public?