The line 「殺しはせん。」 is said by a character in anime.
What is せん here (I assume it's somehow related to negative form of する)?
Plain negative (I'm not killing you)? Volitional neg. (I'm not intending to kill you (like the せん in (せんとする))? Potential (like in せねば…)? Is the ん some auxiliary verb or part of する conjugation?