That’s because homicide is a noun, not a verb. You can kill something, but you can’t homicide something. Darn those pesky semantics. I pray that you are never in front of a jury of your peers that don’t know the difference.
Last year on a grand jury in my county I remember us being warned by the DA to avoid this disease when discussing the case among ourselves. It was for nothing, this warning. Everyone is a legal expert, who knows the difference between a murder and a fourth degree involuntary vehicular homicide. Contemptible social phenomena.