Kirsten was out one day at a bar, and he came across a anthro like him being harrassed. He got kinda ticked. When he was fighting the dude who was hurting the anthro after a long argument, he accidentally unlocked his latent element. Fire. With all his rage, he burnt the person, not killing them, but damaging them enought that they were out like a light. He ended up getting scared of himself, and he only used his power from then on for deadly situations.
maybe the light should be more wellow/orange if the flame is the origine.