You'd been careful. Vampires who tried to be good people had to be. You had been clean of human blood for years at this point. Getting by on cattle blood was humiliating along with disgusting, but it was the right thing to do. You wouldn't murder anymore innocent humans, you couldn't stomach the thought.
Just because you were a monster didn't mean that you had to do monstrous things.
Being careful wasn't easy though. The random strings of cattle mutilations often attracted the attention of Hunters. It never mattered though. You'd cut back on the blood until the hunter left town, and then you'd be halfway across the country. It worked.
That was until Dean Winchester discovered your trail. He has been tracking you for months. It was like a game of cat and mouse. You were usually able to escape him. Usually.
That was until he cornered you in the barn you had attempted hiding in. He had been oddly suspicious of the lack of human victims. He still needed confirmation that you didn't take any human lives.
"Goddamn. Do you have any idea how long I've been tracking you?" He asks, a slow smile spreading across his face.