Ethan simply said, "Yeah, finally managed to catch the guy." He didn't mention how this guy was going around killing other serial killers. He also didn't tell Niki that if it were completely up to him he would have just let this guy keep going. No reason to keep those psychopath's on the streets, right? But, in the end Ethan had had a job to do so he did it.
He continued to listen to her, and though he didn't want to completely believe her, there was that gnawing in the back of his mind that all of this was true. It wouldn't be going away no matter how many weak tissued excuses he hit it with. "If that's the case then I'm going to have to learn how to deal with them, won't I?"
He took another drink, and answered, "As alright as a guy who hasn't sleep in nearly 48 hours."