http://edition.cnn.com/2012/04/24/world/americas/brazil-actor-hanging/index.html

Sad story, but please read the last two paragraph about someone going to a sandwitch cart owner asking for a knife to cut the rope.

I bet nobody around carried a knife because of Brazil's knife laws. The guy in the sandwich cart had a knife because it was a necessary tool for his job, and that's how the actors knew to ask that guy. If a person is carrying a knife in Brazil as a general principle, then the authorities will likely consider it a weapon and "arma branca". Basically, carrying a pocket knife is more trouble than it's worth, except of course if you're accidentally hanging yourself.

On a related note, a neck lanyard must have a breakaway for me to wear it.