Why is the ending of Daybreakers so gory and bloody?

ok so, i was reading the review of the movie Daybreakers and it said that the ending/finale was very very gory, and it was the bloodiest part of the movie. What happens that could be so bloody? and please try to tell me without ruining it for me because i haven't seen it but i just got the movie so im planning too, but im just really curious. thanks.