I mean he was literally the guy who could give them the code? I get he wasn’t talking but instead of shooting him in the head why not bring up guests and tell him “you can either give me the code or you can watch me blow your friends brains out”
shareI guess they felt he was useless alive. They had already tried to scare him, to no avail. Now they could only use his death to threaten the others into cooperating. Plus, the bet.
shareThey no longer needed him. Theo could open the vault it would just take longer that way.
Once they revealed their true motives, he became a liability rather than an asset to them.