If your travelling companion developed a sudden mental illness, would you tie and gag him?

Would you restrain your travelling companion if he went mental, before alerting hotel security, or would you just let him leave the hotel going who knows where? Is there some blanket United Nations rule for this or does it go according to which country you are in?
To Paul M: With respect, mentally ill people don't learn from their mistakes.

it's your companion , a good friend? i would let them go on their own and let what happens , happen , there is no laws to say you are responsible for them if they are of age

Are you crazy? Of course, I would call or take the person to the emergency room IMMEDIATELY!

Eh, let him do what he want. If he wants to act crazy let him.

He'll learn from his mistakes

No I wouldn't restrain anyone. This person could sue you later. Some people have been known to do weird things like that. Unless your the guy, who actually saved this guys life by jumping before a train. Holding the person down, while the train is going over the two of them. The dude on top of this guy almost got killed trying to save the other guys life. Because the guy being restrain was pushing the dude up into the moving train. Even when the train stopped this guy didn't care. He just wanted up! The cops said to restrain him until they could help. Unbelievable. Yea- I think someone can sue. Then again you could get in trouble if you were to leave. The best thing to do is dial 911.

"First I would make him drink a gallon of anti-freeze. Then... I would force him to the ground and dance all around him chanting, "House on fire! House on fire!" Then.... [deleted] And in the morning he would wake up in excruciating pain with a size seven poop shoot" - Phil Hartman SNL

I'm sorry to hear your friend went mental and all that. I would grab his passport, turn it over to the authorities notifying them of his condition. But... I would not restrain him or try to improvise electro-shock therapy.

mental illness is only recognized by others, so let someone with the knowledge to handle it... If its a friend you should have already known about this and how to handle it...The rule is never leave a friend behind!!!