There are only so many ways you can react to a scenario like this. Humour is better. Humour makes it bearable if only for a bit.

"You attacked the person who was attacking him?. Huh." Talk about mugging the murderer. He keeps his ears out for any strange sounds, like footsteps or, preferably, a car coming their way, but he can focus enough on her to keep a conversation going. "Pretty brave of you. Kind of reckless too if I can add that. Looks like they were going at it when you decided to step in."

Matthew hopes that she didn't get a good look of the person's face or the person doesn't realise it if that's the case. Last thing she needs is a target on her back. "You have someone to call if the coppers go ahead and try to stir shit with you, right?"