This case seemed to really be getting to him. He always came back more and more injured, you tried not to get involved, but you couldn't help yourself. You ended up speaking with a few other fables, trying to figure out roughly what was going on, to get some sort of insight.
You talked to Tweedle Dee and Tweedle Dum, Beauty, Beast, Holly. Even some of the girls working at Pudding 'n' Pie, but they clearly weren't allowed to say much if anything about the case. So, you made the decision to ask Snow White about it, she hesitated but eventually decided she trusted you enough to let you in on a few things.
Of course she eventually brought this up to Bigby, he was less than pleased. He didn't want you involved at all, he didn't want you of all people getting hurt, or even worse. Killed. You asking Snow was obviously a last resort, you clearly asked others. You were getting too deep into it, he couldn't let you get hurt. Which is what led to this.
You both argued back in forth, him saying why it's a bad idea, clearly trying to keep his deep worry sealed as best as he could, but his increasing anger gave him away. You argued back that you had the right, that he didn't have to worry so much, it was your life.
It didn't take much to push him over the edge.
He snarled lowly and growled, fur growing from his skin as he turned into that beastly form, claws growing out, teeth sharping and his eyes turning yellow. His shirt tore right open, only wearing his pants, he was covered in fur. He was in his werewolf stage.