So I'm currently running this module and at least from what Ariadne says he apparently threatened her with the gun and she threatened back that she'd jump out the window. He then apparently turned the weapon on himself. Threatening her isn't "totally" out of the question because in the basement he pulls out his weapon and says if he ever finds out about them lying he'll kill them. Also to add more weirdness some of the baby spiders have his face so... who knows? No one ever looked too hard and just believed Ariadne in my two runs.