Horror anime about vampires hunted down by humans
It sounds like Shiki:




  When citizens of a secluded village begin dying off in alarming numbers, the sole hospital's head doctor tries desperately to save his patients—but his efforts are in vain. Entire families are wiped out while others desert their homes. All hell breaks loose as the villagers discover their loved ones' corpses are rising from the grave with an insatiable thirst for human blood. Who is safe when the urge to kill in order to survive blurs the line between man and monster?



It is pretty gruesome especially in showing humans killing vampires
In the beginning of the series vampires kills humans without letting them realize they were actually killed (they just considered theirs as unexplained deaths)... When humans realize the existence of vampires they begin to hunt them down.
I think the scene you described is taken from Episode 20.5: here is a clip from that episode.