Shortly after being turned into a vampire, Klaus made his first human kill, which resulted in Esther's darkest secret coming to light; Klaus was not Mikael's son, but instead was the product of an affair Esther had with the Alpha of their village's werewolf pack, Ansel.
Beneath the area was a series of tunnels that provided protection for the humans while the werewolves were turned on the full moon.
A werewolf who has yet to trigger his or her curse only exhibits one characteristic of lycanthropy: increased aggression and anger on a general basis, which can become overwhelming fits of violent rage leading up to and during the nights of the full moon.
Also, until their werewolf genes are activated, untriggered werewolves can be compelled by vampires just like any human, as proven when Damon Salvatore was easily able to compel away Tyler Lockwood's memories of seeing Vicki Donovan "vamped-out" before Tyler had triggered his werewolf gene.
Werewolves will attack humans, but instinct and centuries of rivalry have hardwired them to hunt their prey of choice -- vampires.
Werewolves (also called Lycanthropes, Loup Garou, Rougarou, Beasts, or even just Wolves for short) are a supernatural shapeshifting species of individuals who unwillingly transform into large, fearsome, and extremely hostile wolves on the night of the full moon.