Thomas LeBlanc was originally a human rapist and serial killer, until he was recruited for the Mutt uprising and was turned into a werewolf.
LeBlanc was an infamous rapist, serial killer, and a consummate misogynist, beholding a seething hatred of women. He kept a scrapbook of his exploits, with details, newspaper clippings, sometimes even trophies that reminded him of each woman he raped and killed.
After joining the Mutts and becoming a werewolf, he would hear of Elena Michaels, but his woman-hating nature caused him to underestimate her and mock her when they first met that Elena put him in his place by breaking his wrist. This caused LeBlanc's hatred to peak as he sought out Elena and attempted to kill her with a gun (even killing a blonde woman whom he mistook for Elena), despite the orders that Elena was supposed to be captured, not killed.
He didn't care about such orders because of his hatred and need to prove himself superior over Elena (and women in general).