Hunter of Night Hunters

So the background is his day job is a traveling Chirurgeon. But really he belongs to a Order of people who hunt monsters of the night. The patron god of the order is a moon goddess. He's a crossbow guy like Van Helsen: So I was thinking Inquisitor/Ace Bolter but I'm having trouble on deciding on his Inquisition.

Edit: Also what is the best class to dip in for Arcane Trickster for that sneak attack. I was looking into Vivisectionist but it just sounds to evil for that character(chaotic or neutral good).