Oh yeah, I've heard of deer just straight up eating birds and shit.
Come to think of it, actually I'm pretty sure hippos are herbivores too? But just like deer they sometimes eat meat. Just thinking about the other reply reminded me of that, earlier Beastars had the hippo in the carnivore camp... but they're not carnivores any more than deer are.
I'm not sure what separates a herbivore that sometimes eats meat and an omnivore, though.
Either way, considering this world already established a lot of carnivores eat people, him eating something doesn't hold any more meaning than that in my books. Eating someone sapient is always kinda fucked up but it's whatever.