Caroline didn't have a whole lot to do in Season 1, but when Katherine Pierce "killed" her in the season finale with Damon's vampire blood in her system and turned her into a vampire, her character was totally revamped (pun intended). ... Like most newly turned vampires, Caroline lost her chill after her first kill.

Why does Katherine turn Caroline into a vampire?

Katherine killed Caroline in order to get a message to the Salvatore brothers. Luckily, Caroline had vampire blood in her system and returned as a vampire. Once Caroline became a vampire, she actually developed as a more interesting and charismatic character but still, Katherine did kill her.

What episode does Caroline turn to a vampire?

2×02 “Brave New World” Since Caroline is a newly turned vampire, she wakes up in the hospital craving blood. She steals a blood bag and drinks it, completing her transition.