Grab and go?
Be a good witness.
Start rounding people up or moving through the dining room?
I access the situation and if it warrants a more proactive stance to ensure the security and safety of me and mine, then it's on.
If the restaurant wanted me to be their security, then they would have hired me. Since they didn't, I'm minding my own business and letting them tend to theirs.
I don't carry to be the Super Secret Bane of Evil Doers Everywhere. I carry to protect me and mine.
NOT you and yours.
NOT them and theirs.
ME. And. Mine.
If, in the course of protecting me and mine, I end up saving you and yours or them and theirs, then that's a fantastic happy coincidence. BUT that's exactly what it is- a happy coincidence.
You can file this one away because that's gonna be my stock answer to any of the normal 'What if...." questions.