Free speech zone??? Not saying it does not exist but I've never heard of that, I've lived in the US my whole life.
In the US you can protest where ever you want as long as you don't, trespass, disrupt business or any sort of proccedings.
The one in San francisco is Anti-china in nature.. allowable.
I read somewhere that they were in running kits, when they were run over.The West? I assume you are including the US. In case you did not know all police in the US whether local, state or Federal are armed.
As far as the attack is concerned it appears to me the the attackers knew when to attack to get the greatest damage to the unsuspecting police. The PAP was unfortunatley caught completly by surprise. I'm sure the PAP will take measures to beef up their own security.
BTW, how were the two arrested ? Obviously, by the surviving cops, when they continued with knive attack. In Normal circumstances, if the cops were armed - firearms would be used. Most likely not all died from just the truck attack.