Coffee's clue was S2/3 possibility. Between your gunshot, my explosion, and the clues from D1, I'm pretty confident we're in S2. Especially since Kas's death lines up with what he told me about his plan in PMs.
EDIT:
S1 Clues: 3 - spike(S3) explosion(S2), gunshot(S2)
S2 Clues: 4 - rithmatic defense (unique), explosion(S1), gunshot(S1), voidlight gemstone(S3)
S3 Clues: 2 - spike(S1), voidlight gemstone(S2)
So it's definitely impossible that we're in S1. We could still be in S3 and Kas was a Kandra, but I doubt it.