A few times I did have success with 'calm' down. But the majority did need a slap in the face or even tougher means. When the panic system in a human is activated the ability to listen is almost lost. Try to stop a stampede. Not that I slapped people. But it would have been effective.I resorted to brutal yelling like in the army. The other means depending on the character is to let people vent the panic by making them do things, like e.g. cleaning, sorting, packing and unpacking.