The sergeant is correct, in a narrow technical sense. However, when it comes to law all there is, is a ‘narrow, technical sense’. The deceased is a ‘victim’ of homicide - defined as the intentional killing of another. He is the ‘victim’ because he was himself the perpetrator of criminal attempt of homicide.
The law provides for justification for reason of defense of oneself or another, which was correctly applied by the authorities here.
So although it sounds in a first reading like the decedent is somehow not responsible for his own demise, that’s not the case. Bad guy tried to shoot his ex lady and her new friends. Intended victims shot better. Cops and prosecutor correctly investigated and applied a just law.
All is well.
Might want to check the Black's Law definition of, "Victim." A justifiable homicide is not a criminal act, and therefore in a, "narrow technical sense," it does not produce a victim.