Answer:
Moral outrage.
Step-by-step explanation:
In the case of any wrong and unfortunate event, the victims always demand and expect justice to be given to them for the pain and suffering they were made to go through. Same case for a murdered parent and the expectation of giving a just punishment to the culprit for the crime.
In wanting death for the killer, the parent's want reflects the punishment goal of moral outrage. This is an emotional reaction stemming from the injustice that has been done or given to them. The feeling that the killer deserves the punishment is, to them, a moral judgment, rightly deserved and also will give them a sense of satisfaction in knowing that their child's killer got his/ her due.