Kinda forced.
@heathecliffe this is just an excuse to get the other girl involved, now she has a reason to investigate the parasites and join the MC on his quest, that's all.
In universe narrative it makes no sense, it is just a random kill in the middle of the street in broad daylight, when by this point they have been organizing in groups and even staging eating grounds.
So forced, and cheap, the author didn't even try.