I doubt the little guy is impressed by the visit, they will naturally investigate shells and new potential homes, if there is someone inside they may try their luck to get him to evacuate.. whenever you see this just keep an eye on them, the smaller one may have died and he is now being snacked on, look to see if the claw is coming to the mouth. If yu are not sure break them up manually and check inside the small shell to make sure all is OK.