Eric pissed off a few of the wrong werewolves and they attacked you. You were dying, the injuries were killing you, bleeding out, lying nearly limp in Eric’s arms. He tried giving you some of his blood, but it wasn’t working.

He was panicking. It’s not like he didn’t know how to turn someone, he’s done it before, he’s just scared. He’s terrified of losing you.

As soon as your pulse stopped, he made the decision to turn you, he couldn’t risk losing you. You were his human, the only one he’s ever felt a true connection towards. He'll be damned if he loses you.