General overview of the verb

  Active Passive Reflexive
Simple קָטַל Qal    נִקְטַל Nifal
  he killed   he killed himselfhe was killed
Intensive קִטֵּל Piel קֻטַּל Pual הִתְקַטֵּל Hitpael
  he killed
intensely
he was killed intensely he killed himself intensely
Causative הִקְטִיל Hifil הָקְטַל Hofal  
  he made kill one has caused him to kill