The affix ṇini comes after the verb han 'to kill' when the word in composition with it is kumāra 'a child' or śīrṣa 'head'.,
The affix णिनि comes after the verb हन् 'to kill' when the word in composition with it is कुमार 'a child', or शीर्ष 'head'.
Thus कुमार + हन् + णिनि = कुमार + घात + इन् 7.3.54 and 7.3.32 = कुमारघातिन् nom. sing. कुमारघाती 'child-killer'. So also शीर्षघातिन् nom. sing. शीर्षघाती 'head-killer'.
The word शीर्ष is an irregular form of the word शिरस् ।,