The speed with which he reacts isn't surprising to Trevor when combined with the other things he witnessed so far. It's rather obvious that this person knows how to take care of themselves even in this kind of situation.
He notes the way he's being observed, the almost unnerving sense of being sized up making Trevor inwardly prepare himself just in case this encounter somehow leads to his being challenged. He hopes the other figure can see that he means no harm, but there's always that chance.
Eyebrows raising at the sound of the fellow whip-wielders' voice, Trevor relaxes subtly as he nods in answer to the question he was asked. "I'm always ready to assist someone in trouble, especially someone from that accursed hotel."
Still unsure of what to think of the other man, he starts walking towards him so he doesn't have to speak as loudly, on the off chance it might attract nearby bugs.